conversion

conversion — convert images in some way: change band format, change header, insert, extract, join

Stability Level

Stable, unless otherwise indicated

Synopsis

#include <vips/vips.h>

DOUBLEMASK *        im_vips2mask                        (VipsImage *in,
                                                         const char *filename);
int                 im_mask2vips                        (DOUBLEMASK *in,
                                                         VipsImage *out);
int                 im_copy                             (VipsImage *in,
                                                         VipsImage *out);
int                 im_copy_set                         (VipsImage *in,
                                                         VipsImage *out,
                                                         VipsInterpretation interpretation,
                                                         float xres,
                                                         float yres,
                                                         int xoffset,
                                                         int yoffset);
int                 im_copy_set_meta                    (VipsImage *in,
                                                         VipsImage *out,
                                                         const char *field,
                                                         GValue *value);
int                 im_copy_morph                       (VipsImage *in,
                                                         VipsImage *out,
                                                         int bands,
                                                         VipsBandFormat format,
                                                         VipsCoding coding);
int                 im_copy_swap                        (VipsImage *in,
                                                         VipsImage *out);
int                 im_copy_native                      (VipsImage *in,
                                                         VipsImage *out,
                                                         gboolean is_msb_first);
int                 im_copy_file                        (VipsImage *in,
                                                         VipsImage *out);
int                 im_clip2fmt                         (VipsImage *in,
                                                         VipsImage *out,
                                                         VipsBandFormat fmt);
int                 im_scale                            (VipsImage *in,
                                                         VipsImage *out);
int                 im_msb                              (VipsImage *in,
                                                         VipsImage *out);
int                 im_msb_band                         (VipsImage *in,
                                                         VipsImage *out,
                                                         int band);
int                 im_c2amph                           (VipsImage *in,
                                                         VipsImage *out);
int                 im_c2rect                           (VipsImage *in,
                                                         VipsImage *out);
int                 im_ri2c                             (VipsImage *in1,
                                                         VipsImage *in2,
                                                         VipsImage *out);
int                 im_c2imag                           (VipsImage *in,
                                                         VipsImage *out);
int                 im_c2real                           (VipsImage *in,
                                                         VipsImage *out);
int                 im_scaleps                          (VipsImage *in,
                                                         VipsImage *out);
int                 im_falsecolour                      (VipsImage *in,
                                                         VipsImage *out);
int                 im_gaussnoise                       (VipsImage *out,
                                                         int x,
                                                         int y,
                                                         double mean,
                                                         double sigma);
int                 im_black                            (VipsImage *out,
                                                         int x,
                                                         int y,
                                                         int bands);
int                 im_text                             (VipsImage *out,
                                                         const char *text,
                                                         const char *font,
                                                         int width,
                                                         int alignment,
                                                         int dpi);
int                 im_extract_band                     (VipsImage *in,
                                                         VipsImage *out,
                                                         int band);
int                 im_extract_bands                    (VipsImage *in,
                                                         VipsImage *out,
                                                         int band,
                                                         int nbands);
int                 im_extract_area                     (VipsImage *in,
                                                         VipsImage *out,
                                                         int left,
                                                         int top,
                                                         int width,
                                                         int height);
int                 im_extract_areabands                (VipsImage *in,
                                                         VipsImage *out,
                                                         int left,
                                                         int top,
                                                         int width,
                                                         int height,
                                                         int band,
                                                         int nbands);
int                 im_embed                            (VipsImage *in,
                                                         VipsImage *out,
                                                         int type,
                                                         int x,
                                                         int y,
                                                         int width,
                                                         int height);
int                 im_bandjoin                         (VipsImage *in1,
                                                         VipsImage *in2,
                                                         VipsImage *out);
int                 im_gbandjoin                        (VipsImage **in,
                                                         VipsImage *out,
                                                         int n);
int                 im_insert                           (VipsImage *main,
                                                         VipsImage *sub,
                                                         VipsImage *out,
                                                         int x,
                                                         int y);
int                 im_insert_noexpand                  (VipsImage *main,
                                                         VipsImage *sub,
                                                         VipsImage *out,
                                                         int x,
                                                         int y);
int                 im_insertset                        (VipsImage *main,
                                                         VipsImage *sub,
                                                         VipsImage *out,
                                                         int n,
                                                         int *x,
                                                         int *y);
int                 im_lrjoin                           (VipsImage *left,
                                                         VipsImage *right,
                                                         VipsImage *out);
int                 im_tbjoin                           (VipsImage *top,
                                                         VipsImage *bottom,
                                                         VipsImage *out);
int                 im_replicate                        (VipsImage *in,
                                                         VipsImage *out,
                                                         int across,
                                                         int down);
int                 im_grid                             (VipsImage *in,
                                                         VipsImage *out,
                                                         int tile_height,
                                                         int across,
                                                         int down);
int                 im_wrap                             (VipsImage *in,
                                                         VipsImage *out,
                                                         int x,
                                                         int y);
int                 im_fliphor                          (VipsImage *in,
                                                         VipsImage *out);
int                 im_flipver                          (VipsImage *in,
                                                         VipsImage *out);
int                 im_rot90                            (VipsImage *in,
                                                         VipsImage *out);
int                 im_rot180                           (VipsImage *in,
                                                         VipsImage *out);
int                 im_rot270                           (VipsImage *in,
                                                         VipsImage *out);
int                 im_subsample                        (VipsImage *in,
                                                         VipsImage *out,
                                                         int xshrink,
                                                         int yshrink);
int                 im_zoom                             (VipsImage *in,
                                                         VipsImage *out,
                                                         int xfac,
                                                         int yfac);
int                 im_system                           (VipsImage *im,
                                                         const char *cmd,
                                                         char **out);
VipsImage *         im_system_image                     (VipsImage *im,
                                                         const char *in_format,
                                                         const char *out_format,
                                                         const char *cmd_format,
                                                         char **log);

Description

These operations convert an image in some way. They can be split into a two main groups.

The first set of operations change an image's format in some way. You can change the band format (for example, cast to 32-bit unsigned int), form complex images from real images, convert images to matrices and back, change header fields, and a few others.

The second group move pixels about in some way. You can flip, rotate, extract, insert and join pairs of images in various ways.

Details

im_vips2mask ()

DOUBLEMASK *        im_vips2mask                        (VipsImage *in,
                                                         const char *filename);

Make a mask from an image. All images are cast to IM_BANDFMT_DOUBLE before processing. There are two cases for handling bands:

If the image has a single band, im_vips2mask() will write a mask the same size as the image.

If the image has more than one band, it must be one pixel high or wide. In this case the output mask uses that axis to represent band values.

See also: im_mask2vips(), im_measure_area().

in :

input image

filename :

name for output mask

Returns :

a DOUBLEMASK with outname set as the name, or NULL on error

im_mask2vips ()

int                 im_mask2vips                        (DOUBLEMASK *in,
                                                         VipsImage *out);

Write a one-band, IM_BANDFMT_DOUBLE image to out based on mask in.

See also: im_vips2mask().

in :

input mask

out :

output image

Returns :

0 on success, -1 on error

im_copy ()

int                 im_copy                             (VipsImage *in,
                                                         VipsImage *out);

Copy an image. VIPS copies images by copying pointers, so this operation is fast, even for very large images.

See also: im_copy(), im_copy_set(), im_copy_morph().

in :

input image

out :

output image

Returns :

0 on success, -1 on error.

im_copy_set ()

int                 im_copy_set                         (VipsImage *in,
                                                         VipsImage *out,
                                                         VipsInterpretation interpretation,
                                                         float xres,
                                                         float yres,
                                                         int xoffset,
                                                         int yoffset);

Copy an image, changing informational header fields on the way.

See also: im_copy().

in :

input image

out :

output image

type :

new VipsType to set

xres :

new Xres to set

yres :

new Yres to set

xoffset :

new Xoffset to set

yoffset :

new Yoffset to set

Returns :

0 on success, -1 on error.

im_copy_set_meta ()

int                 im_copy_set_meta                    (VipsImage *in,
                                                         VipsImage *out,
                                                         const char *field,
                                                         GValue *value);

Copy an image, changing a metadata field. You can use this to, for example, update the ICC profile attached to an image.

See also: im_copy().

in :

input image

out :

output image

field :

metadata field to set

value :

value to set for the field

Returns :

0 on success, -1 on error.

im_copy_morph ()

int                 im_copy_morph                       (VipsImage *in,
                                                         VipsImage *out,
                                                         int bands,
                                                         VipsBandFormat format,
                                                         VipsCoding coding);

Copy an image, changing header fields which alter pixel addressing. The pixel data itself is unchanged, this operation just changes the header fields.

If you change the header fields such that the sizeof() a pixel changes, you'll get an error.

See also: im_copy().

in :

input image

out :

output image

bands :

new number of bands

bandfmt :

new band format

coding :

new coding

Returns :

0 on success, -1 on error.

im_copy_swap ()

int                 im_copy_swap                        (VipsImage *in,
                                                         VipsImage *out);

Copy an image, swapping byte order between little and big endian. This really does change image pixels and does not just alter the header.

See also: im_copy(), im_amiMSBfirst(), im_isMSBfirst().

in :

input image

out :

output image

Returns :

0 on success, -1 on error.

im_copy_native ()

int                 im_copy_native                      (VipsImage *in,
                                                         VipsImage *out,
                                                         gboolean is_msb_first);

Copy an image to native order, that is, the order for the executing program.

See also: im_copy_swap(), im_amiMSBfirst().

in :

input image

out :

output image

is_msb_first :

TRUE if in is in most-significant first form

Returns :

0 on success, -1 on error.

im_copy_file ()

int                 im_copy_file                        (VipsImage *in,
                                                         VipsImage *out);

Copy an image to a disc file, then copy again to output. If the image is already a disc file, just copy straight through.

The disc file is allocated in the same way as im_system_image(). The file is automatically deleted when out is closed.

See also: im_copy(), im_system_image().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_clip2fmt ()

int                 im_clip2fmt                         (VipsImage *in,
                                                         VipsImage *out,
                                                         VipsBandFormat fmt);

Convert in to fmt format. You can convert between any pair of formats. Floats are truncated (not rounded). Out of range values are clipped.

See also: im_scale(), im_ri2c().

in :

input image

out :

output image

fmt :

format to convert to

Returns :

0 on success, -1 on error

im_scale ()

int                 im_scale                            (VipsImage *in,
                                                         VipsImage *out);

Search the image for the maximum and minimum value, then return the image as unsigned 8-bit, scaled so that the maximum value is 255 and the minimum is zero.

See also: im_clip2fmt(), im_scaleps().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_msb ()

int                 im_msb                              (VipsImage *in,
                                                         VipsImage *out);

Turn any integer image to 8-bit unsigned char by discarding all but the most significant byte. Signed values are converted to unsigned by adding 128.

This operator also works for LABQ coding.

See also: im_msb_band().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_msb_band ()

int                 im_msb_band                         (VipsImage *in,
                                                         VipsImage *out,
                                                         int band);

Turn any integer image to a single-band 8-bit unsigned char by discarding all but the most significant byte from the selected band. Signed values are converted to unsigned by adding 128.

This operator also works for LABQ coding.

See also: im_msb_band().

in :

input image

out :

output image

band :

select this band

Returns :

0 on success, -1 on error

im_c2amph ()

int                 im_c2amph                           (VipsImage *in,
                                                         VipsImage *out);

Convert a complex image from rectangular to polar coordinates. Angles are expressed in degrees.

See also: im_c2rect(), im_abs().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_c2rect ()

int                 im_c2rect                           (VipsImage *in,
                                                         VipsImage *out);

Convert a complex image from polar to rectangular coordinates. Angles are expressed in degrees.

See also: im_c2amph().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_ri2c ()

int                 im_ri2c                             (VipsImage *in1,
                                                         VipsImage *in2,
                                                         VipsImage *out);

Compose two real images to make a complex image. If either in1 or in2 are IM_BANDFMT_DOUBLE, out is IM_BANDFMT_DPCOMPLEX. Otherwise out is IM_BANDFMT_COMPLEX. in1 becomes the real component of out and in2 the imaginary.

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

See also: im_c2real(), im_c2imag().

in1 :

input image

in2 :

input image

out :

output image

Returns :

0 on success, -1 on error

im_c2imag ()

int                 im_c2imag                           (VipsImage *in,
                                                         VipsImage *out);

Extract the imaginary part of a complex image.

See also: im_c2real().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_c2real ()

int                 im_c2real                           (VipsImage *in,
                                                         VipsImage *out);

Extract the real part of a complex image.

See also: im_c2imag().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_scaleps ()

int                 im_scaleps                          (VipsImage *in,
                                                         VipsImage *out);

Scale a power spectrum. Transform with log10(1.0 + pow(x, 0.25)) + .5, then scale so max == 255.

See also: im_scale().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_falsecolour ()

int                 im_falsecolour                      (VipsImage *in,
                                                         VipsImage *out);

Force in to 1 band, 8-bit, then transform to 3-band 8-bit image with a false colour map. The map is supposed to make small differences in brightness more obvious.

See also: im_maplut().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_gaussnoise ()

int                 im_gaussnoise                       (VipsImage *out,
                                                         int x,
                                                         int y,
                                                         double mean,
                                                         double sigma);

Make a one band float image of gaussian noise with the specified distribution. The noise distribution is created by averaging 12 random numbers with the appropriate weights.

See also: im_addgnoise(), im_make_xy(), im_text(), im_black().

out :

output image

x :

output width

y :

output height

mean :

average value in output

sigma :

standard deviation in output

Returns :

0 on success, -1 on error

im_black ()

int                 im_black                            (VipsImage *out,
                                                         int x,
                                                         int y,
                                                         int bands);

Make a black unsigned char image of a specified size.

See also: im_make_xy(), im_text(), im_gaussnoise().

out :

output IMAGE

x :

output width

y :

output height

bands :

number of output bands

Returns :

0 on success, -1 on error

im_text ()

int                 im_text                             (VipsImage *out,
                                                         const char *text,
                                                         const char *font,
                                                         int width,
                                                         int alignment,
                                                         int dpi);

Draw the string text to an image. out is a one-band 8-bit unsigned char image, with 0 for no text and 255 for text. Values inbetween are used for anti-aliasing.

text is the text to render as a UTF-8 string. It can contain Pango markup, for example "<i>The</i>Guardian".

font is the font to render with, selected by fontconfig. Examples might be "sans 12" or perhaps "bitstream charter bold 10".

width is the maximum number of pixels across to draw within. If the generated text is wider than this, it will wrap to a new line. In this case, alignment can be used to set the alignment style for multi-line text. 0 means left-align, 1 centre, 2 right-align.

dpi sets the resolution to render at. "sans 12" at 72 dpi draws characters approximately 12 pixels high.

See also: im_make_xy(), im_black(), im_gaussnoise().

out :

output image

text :

utf-8 text string to render

font :

font to render with

width :

render within this many pixels across

alignment :

left/centre/right alignment

dpi :

render at this resolution

Returns :

0 on success, -1 on error

im_extract_band ()

int                 im_extract_band                     (VipsImage *in,
                                                         VipsImage *out,
                                                         int band);

Extract a single band from an image. Extracting outside in will trigger an error.

See also: im_bandjoin().

in :

input image

out :

output image

band :

band to extract

Returns :

0 on success, -1 on error

im_extract_bands ()

int                 im_extract_bands                    (VipsImage *in,
                                                         VipsImage *out,
                                                         int band,
                                                         int nbands);

Extract a number of bands from an image. Extracting outside in will trigger an error.

See also: im_bandjoin().

in :

input image

out :

output image

band :

first band to extract

nbands :

number of bands to extract

Returns :

0 on success, -1 on error

im_extract_area ()

int                 im_extract_area                     (VipsImage *in,
                                                         VipsImage *out,
                                                         int left,
                                                         int top,
                                                         int width,
                                                         int height);

Extract an area from an image. Extracting outside in will trigger an error.

See also: im_embed(), im_insert(), im_extract_bands().

in :

input image

out :

output image

left :

left edge of rectangle

top :

top edge of rectangle

width :

width of rectangle

height :

height of rectangle

Returns :

0 on success, -1 on error

im_extract_areabands ()

int                 im_extract_areabands                (VipsImage *in,
                                                         VipsImage *out,
                                                         int left,
                                                         int top,
                                                         int width,
                                                         int height,
                                                         int band,
                                                         int nbands);

Extract an area and a number of bands from an image. Bands number from zero. Extracting outside in will trigger an error.

See also: im_embed(), im_insert(), im_extract_area(), im_extract_bands().

in :

input image

out :

output image

left :

left edge of rectangle

top :

top edge rectangle

width :

width of rectangle

height :

height of rectangle

band :

first band to extract

nbands :

number of bands to extract

Returns :

0 on success, -1 on error

im_embed ()

int                 im_embed                            (VipsImage *in,
                                                         VipsImage *out,
                                                         int type,
                                                         int x,
                                                         int y,
                                                         int width,
                                                         int height);

The opposite of im_extract(): embed an image within a larger image. type controls what appears in the new pels:

0 black pels (all bytes == 0)
1 extend pels from image edge
2 repeat image
3 mirror image
4 white pels (all bytes == 255)

See also: im_extract_area(), im_insert().

in :

input image

out :

output image

type :

how to generate the edge pixels

x :

place in at this x position in out

y :

place in at this y position in out

width :

out should be this many pixels across

height :

out should be this many pixels down

Returns :

0 on success, -1 on error.

im_bandjoin ()

int                 im_bandjoin                         (VipsImage *in1,
                                                         VipsImage *in2,
                                                         VipsImage *out);

Join two images bandwise. If the two images have n and m bands respectively, then the output image will have n + m bands, with the first n coming from the first image and the last m from the second.

If the images differ in size, the smaller image is enlarged to match the larger by adding zero pixels along the bottom and right.

The two input images are cast up to the smallest common type (see table Smallest common format in arithmetic).

See also: im_gbandjoin(), im_insert().

in1 :

first input image

in2 :

second input image

out :

output image

Returns :

0 on success, -1 on error

im_gbandjoin ()

int                 im_gbandjoin                        (VipsImage **in,
                                                         VipsImage *out,
                                                         int n);

Join a set of images together, bandwise. If the images have n and m bands, then the output image will have n + m bands, with the first n coming from the first image and the last m from the second.

If the images differ in size, the smaller images are enlarged to match the larger by adding zero pixels along the bottom and right.

The input images are cast up to the smallest common type (see table Smallest common format in arithmetic).

See also: im_bandjoin(), im_insert().

in :

vector of input images

out :

output image

n :

number of input images

Returns :

0 on success, -1 on error

im_insert ()

int                 im_insert                           (VipsImage *main,
                                                         VipsImage *sub,
                                                         VipsImage *out,
                                                         int x,
                                                         int y);

Insert one image into another. sub is inserted into image main at position x, y relative to the top LH corner of main. out is made large enough to hold both main and sub. Any areas of out not coming from either main or sub are set to black (binary 0). If sub overlaps main, sub will appear on top of main.

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

The two input images are cast up to the smallest common type (see table Smallest common format in arithmetic).

See also: im_insert_noexpand(), im_lrjoin().

main :

big image

sub :

small image

out :

output image

x :

left position of sub

y :

top position of sub

Returns :

0 on success, -1 on error

im_insert_noexpand ()

int                 im_insert_noexpand                  (VipsImage *main,
                                                         VipsImage *sub,
                                                         VipsImage *out,
                                                         int x,
                                                         int y);

Insert one image into another. sub is inserted into image main at position x, y relative to the top LH corner of main. out is the same size as main. sub is clipped against the edges of main.

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

The two input images are cast up to the smallest common type (see table Smallest common format in arithmetic).

See also: im_insert_noexpand(), im_lrjoin(), im_draw_image().

main :

big image

sub :

small image

out :

output image

x :

left position of sub

y :

top position of sub

Returns :

0 on success, -1 on error

im_insertset ()

int                 im_insertset                        (VipsImage *main,
                                                         VipsImage *sub,
                                                         VipsImage *out,
                                                         int n,
                                                         int *x,
                                                         int *y);

Insert sub repeatedly into main at the positions listed in the arrays x, y of length n. out is the same size as main. sub is clipped against the edges of main.

This operation is fast for large n, but will use a memory buffer the size of out. It's useful for things like making scatter plots.

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

The two input images are cast up to the smallest common type (see table Smallest common format in arithmetic).

See also: im_insert(), im_lrjoin().

main :

big image

sub :

small image

out :

output image

n :

number of positions

x :

left positions of sub

y :

top positions of sub

Returns :

0 on success, -1 on error

im_lrjoin ()

int                 im_lrjoin                           (VipsImage *left,
                                                         VipsImage *right,
                                                         VipsImage *out);

Join left and right together, left-right. If one is taller than the other, out will be has high as the smaller.

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

The two input images are cast up to the smallest common type (see table Smallest common format in arithmetic).

See also: im_insert(), im_tbjoin().

left :

image to go on left

right :

image to go on right

out :

output image

Returns :

0 on success, -1 on error

im_tbjoin ()

int                 im_tbjoin                           (VipsImage *top,
                                                         VipsImage *bottom,
                                                         VipsImage *out);

Join top and bottom together, up-down. If one is wider than the other, out will be has wide as the smaller.

If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.

The two input images are cast up to the smallest common type (see table Smallest common format in arithmetic).

See also: im_insert(), im_tbjoin().

top :

image to go on top

bottom :

image to go on bottom

out :

output image

Returns :

0 on success, -1 on error

im_replicate ()

int                 im_replicate                        (VipsImage *in,
                                                         VipsImage *out,
                                                         int across,
                                                         int down);

Replicate an image x times horizontally and vertically.

See also: im_embed(), im_copy().

in :

input image

out :

output image

across :

repeat in this many times across

down :

repeat in this many times down

Returns :

0 on success, -1 on error.

im_grid ()

int                 im_grid                             (VipsImage *in,
                                                         VipsImage *out,
                                                         int tile_height,
                                                         int across,
                                                         int down);

Chop a tall thin image up into a set of tiles, lay the tiles out in a grid.

The input image should be a very tall, thin image containing a list of smaller images. Volumetric or time-sequence images are often laid out like this. This image is chopped into a series of tiles, each tile_height pixels high and the width of in. The tiles are then rearranged into a grid across tiles across and down tiles down in row-major order.

See also: im_embed(), im_insert(), im_lrjoin().

in :

input image

out :

output image

tile_height :

chop into tiles this high

across :

tiles across

down :

tiles down

Returns :

0 on success, -1 on error

im_wrap ()

int                 im_wrap                             (VipsImage *in,
                                                         VipsImage *out,
                                                         int x,
                                                         int y);

Slice an image up and move the segments about so that the pixel that was at 0, 0 is now at x, y.

See also: im_embed(), im_replicate(), im_rotquad().

in :

input image

out :

output image

x :

horizontal displacement

y :

vertical displacement

Returns :

0 on success, -1 on error

im_fliphor ()

int                 im_fliphor                          (VipsImage *in,
                                                         VipsImage *out);

Flips an image left-right.

See also: im_flipver(), im_rot90().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_flipver ()

int                 im_flipver                          (VipsImage *in,
                                                         VipsImage *out);

Flips an image top-bottom.

See also: im_fliphor(), im_rot90().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_rot90 ()

int                 im_rot90                            (VipsImage *in,
                                                         VipsImage *out);

Rotate an image 90 degrees.

See also: im_rot180(), im_rot270(), im_affinei_all().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_rot180 ()

int                 im_rot180                           (VipsImage *in,
                                                         VipsImage *out);

Rotate an image 180 degrees.

See also: im_rot90(), im_rot270(), im_affinei_all().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_rot270 ()

int                 im_rot270                           (VipsImage *in,
                                                         VipsImage *out);

Rotate an image 270 degrees.

See also: im_rot180(), im_rot90(), im_affinei_all().

in :

input image

out :

output image

Returns :

0 on success, -1 on error

im_subsample ()

int                 im_subsample                        (VipsImage *in,
                                                         VipsImage *out,
                                                         int xshrink,
                                                         int yshrink);

Subsample an image by an integer fraction. This is fast nearest-neighbour shrink.

See also: im_shrink(), im_affinei(), im_zoom().

in :

input image

out :

output image

xshrink :

horizontal shrink factor

yshrink :

vertical shrink factor

Returns :

0 on success, -1 on error.

im_zoom ()

int                 im_zoom                             (VipsImage *in,
                                                         VipsImage *out,
                                                         int xfac,
                                                         int yfac);

Zoom an image by repeating pixels. This is fast nearest-neighbour zoom.

See also: im_affinei(), im_subsample().

in :

input image

out :

output image

xfac :

horizontal scale factor

yfac :

vertical scale factor

Returns :

0 on success, -1 on error.

im_system ()

int                 im_system                           (VipsImage *im,
                                                         const char *cmd,
                                                         char **out);

im_system() runs a command on an image, returning the command's output as a string. The command is executed with popen(), the first '%s' in the command being substituted for a filename.

If the IMAGE is a file on disc, then the filename will be the name of the real file. If the image is in memory, or the result of a computation, then a new file is created in the temporary area called something like "vips_XXXXXX.v", and that filename given to the command. The file is deleted when the command finishes.

See im_system_image() for details on how VIPS selects a temporary directory.

In all cases, log must be freed with im_free().

See also: im_system_image().

im :

image to run command on

cmd :

command to run

out :

stdout of command is returned here

Returns :

0 on success, -1 on error

im_system_image ()

VipsImage *         im_system_image                     (VipsImage *im,
                                                         const char *in_format,
                                                         const char *out_format,
                                                         const char *cmd_format,
                                                         char **log);

im_system_image() runs a command, passing an image in and getting an image back. The command's stdout is returned in log.

First, im is written to a file. The filename is formed by substituting something like "vips-49857-1" for the first %s in in_format, then prepending "/tmp". If the environment variable TMPDIR is defined, it can be used to set a different temporary directory. If in_format is something like "%s.png", the file will be written in PNG format.

On Windows, if the environment variable TMPDIR is not defined, VIPS calls GetTempPath() to get the user's preferred temporary area. If that fails, it defaults to C:\temp.

Next an output filename is created in the same way using out_format. The command string to run is made by substituting the first %s in cmd_format for the name of the input file and the second %s for the output filename.

The command is executed with popen() and the output captured in log. If the command fails, the temporary files are deleted and im_system_image() returns NULL. log is still set.

If the command succeeds, the input file is deleted, the output file opened, and returned. Closing the output image will automatically delete the file.

In all cases, log must be freed with im_free().

For example, this call will run the ImageMagick convert program on an image, using JPEG files to pass images into and out of the convert command.

im_system_image( in, out, 
  "%s.jpg", "%s.jpg", "convert %s -swirl 45 %s", 
  &log )

See also: im_system().

im :

image to run command on

in_format :

write input file like this

out_format :

write output filename like this

cmd_format :

command to run

log :

stdout of command is returned here

Returns :

an image on success, NULL on error

See Also

resample