libvips

vips_copy ()

int
vips_copy (VipsImage *in,
           VipsImage **out,
           ...);

Optional arguments:

Copy an image, optionally modifying the header. VIPS copies images by copying pointers, so this operation is instant, even for very large images.

You can optionally change any or all header fields during the copy. You can make any change which does not change the size of a pel, so for example you can turn a 4-band uchar image into a 2-band ushort image, but you cannot change a 100 x 100 RGB image into a 300 x 100 mono image.

See also: vips_byteswap(), vips_bandfold(), vips_bandunfold().

[method]

vips_tilecache ()

int
vips_tilecache (VipsImage *in,
                VipsImage **out,
                ...);

Optional arguments:

This operation behaves rather like vips_copy() between images in and out , except that it keeps a cache of computed pixels. This cache is made of up to max_tiles tiles (a value of -1 means any number of tiles), and each tile is of size tile_width by tile_height pixels.

Each cache tile is made with a single call to vips_region_prepare().

When the cache fills, a tile is chosen for reuse. If access is VIPS_ACCESS_RANDOM, then the least-recently-used tile is reused. If access is VIPS_ACCESS_SEQUENTIAL the top-most tile is reused.

By default, tile_width and tile_height are 128 pixels, and the operation will cache up to 1,000 tiles. access defaults to VIPS_ACCESS_RANDOM.

Normally, only a single thread at once is allowed to calculate tiles. If you set threaded to TRUE, vips_tilecache() will allow many threads to calculate tiles at once, and share the cache between them.

Normally the cache is dropped when computation finishes. Set persistent to TRUE to keep the cache between computations.

See also: vips_cache(), vips_linecache().

[method]

vips_linecache ()

int
vips_linecache (VipsImage *in,
                VipsImage **out,
                ...);

Optional arguments:

This operation behaves rather like vips_copy() between images in and out , except that it keeps a cache of computed scanlines.

The number of lines cached is enough for a small amount of non-local access.

Each cache tile is made with a single call to vips_region_prepare().

When the cache fills, a tile is chosen for reuse. If access is VIPS_ACCESS_RANDOM, then the least-recently-used tile is reused. If access is VIPS_ACCESS_SEQUENTIAL, then the top-most tile is reused. access defaults to VIPS_ACCESS_RANDOM.

tile_height can be used to set the size of the strips that vips_linecache() uses. The default is 1 (a single scanline).

Normally, only a single thread at once is allowed to calculate tiles. If you set threaded to TRUE, vips_linecache() will allow many threads to calculate tiles at once and share the cache between them.

See also: vips_cache(), vips_tilecache().

[method]

vips_sequential ()

int
vips_sequential (VipsImage *in,
                 VipsImage **out,
                 ...);

Optional arguments:

This operation behaves rather like vips_copy() between images in and out , except that it checks that pixels on in are only requested top-to-bottom. This operation is useful for loading file formats which are strictly top-to-bottom, like PNG.

strip_height can be used to set the size of the tiles that vips_sequential() uses. The default value is 1.

See also: vips_cache(), vips_linecache(), vips_tilecache().

[method]

vips_cache ()

int
vips_cache (VipsImage *in,
            VipsImage **out,
            ...);

Optional arguments:

This operation behaves rather like vips_copy() between images in and out , except that it keeps a cache of computed pixels. This cache is made of up to max_tiles tiles (a value of -1 means any number of tiles), and each tile is of size tile_width by tile_height pixels. By default it will cache 250 128 x 128 pixel tiles, enough for two 1920 x 1080 images.

This operation is a thin wrapper over vips_sink_screen(), see the documentation for that operation for details.

It uses a set of background threads to calculate pixels and the various active cache operations coordinate so as not to overwhelm your system. When a request is made for an area of pixels, the operation will block until all of those pixels have been calculated. Pixels are calculated with a set of threads.

See also: vips_tilecache().

[method]

vips_copy_file ()

int
vips_copy_file (VipsImage *in,
                VipsImage **out,
                ...);

A simple convenience function to copy an image to a file, then copy again to output. If the image is already a file, just copy straight through.

The file is allocated with vips_image_new_temp_file(). The file is automatically deleted when out is closed.

See also: vips_copy(), vips_image_new_temp_file().

[method]

vips_embed ()

int
vips_embed (VipsImage *in,
            VipsImage **out,
            int x,
            int y,
            int width,
            int height,
            ...);

Optional arguments:

The opposite of vips_extract_area(): embed in within an image of size width by height at position x , y .

extend controls what appears in the new pels, see VipsExtend.

See also: vips_extract_area(), vips_insert().

[method]

vips_gravity ()

int
vips_gravity (VipsImage *in,
              VipsImage **out,
              VipsCompassDirection direction,
              int width,
              int height,
              ...);

Optional arguments:

The opposite of vips_extract_area(): place in within an image of size width by height at a certain gravity.

extend controls what appears in the new pels, see VipsExtend.

See also: vips_extract_area(), vips_insert().

vips_flip ()

int
vips_flip (VipsImage *in,
           VipsImage **out,
           VipsDirection direction,
           ...);

Flips an image left-right or up-down.

See also: vips_rot().

[method]

vips_insert ()

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

Optional arguments:

Insert sub into main at position x , y .

Normally out shows the whole of main . If expand is TRUE then out is made large enough to hold all of main and sub . Any areas of out not coming from either main or sub are set to background (default 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

See also: vips_join(), vips_embed(), vips_extract_area().

[method]

vips_join ()

int
vips_join (VipsImage *in1,
           VipsImage *in2,
           VipsImage **out,
           VipsDirection direction,
           ...);

Optional arguments:

Join in1 and in2 together, left-right or up-down depending on the value of direction .

If one is taller or wider than the other, out will be has high as the smaller. If expand is TRUE, then the output will be expanded to contain all of the input pixels.

Use align to set the edge that the images align on. By default, they align on the edge with the lower value coordinate.

Use background to set the colour of any pixels in out which are not present in either in1 or in2 .

Use shim to set the spacing between the images. By default this is 0.

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

If you are going to be joining many thousands of images in a regular grid, vips_arrayjoin() is a better choice.

See also: vips_arrayjoin(), vips_insert().

vips_arrayjoin ()

int
vips_arrayjoin (VipsImage **in,
                VipsImage **out,
                int n,
                ...);

Optional arguments:

Lay out the images in in in a grid. The grid is across images across and however high is necessary to use up all of in . Images are set down left-to-right and top-to-bottom. across defaults to n .

Each input image is placed with a box of size hspacing by vspacing pixels and cropped. These default to the largest width and largest height of the input images.

Space between images is filled with background . This defaults to 0 (black).

Images are positioned within their hspacing by vspacing box at low, centre or high coordinate values, controlled by halign and valign . These default to left-top.

Boxes are joined and separated by shim pixels. This defaults to 0.

If the number of bands in the input images differs, all but 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 n-band images are operated upon.

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

See also: vips_join(), vips_insert().

vips_extract_area ()

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

Extract an area from an image. The area must fit within in .

See also: vips_extract_bands(), vips_smartcrop().

[method]

vips_crop ()

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

A synonym for vips_extract_area().

See also: vips_extract_bands(), vips_smartcrop().

[method]

vips_smartcrop ()

int
vips_smartcrop (VipsImage *in,
                VipsImage **out,
                int width,
                int height,
                ...);

Optional arguments:

Crop an image down to a specified width and height by removing boring parts.

Use interesting to pick the method vips uses to decide which bits of the image should be kept.

You can test xoffset / yoffset on out to find the location of the crop within the input image.

See also: vips_extract_area().

[method]

vips_extract_band ()

int
vips_extract_band (VipsImage *in,
                   VipsImage **out,
                   int band,
                   ...);

Optional arguments:

Extract a band or bands from an image. Extracting out of range is an error.

See also: vips_extract_area().

[method]

vips_replicate ()

int
vips_replicate (VipsImage *in,
                VipsImage **out,
                int across,
                int down,
                ...);

Repeats an image many times.

See also: vips_extract_area().

[method]

vips_grid ()

int
vips_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.

Supplying tile_height , across and down is not strictly necessary, we only really need two of these. Requiring three is a double-check that the image has the expected geometry.

See also: vips_embed(), vips_insert(), vips_join().

[method]

vips_transpose3d ()

int
vips_transpose3d (VipsImage *in,
                  VipsImage **out,
                  ...);

Optional arguments:

page_height : gint, size of each input page

Transpose a volumetric image.

Volumetric images are very tall, thin images, with the metadata item VIPS_META_PAGE_HEIGHT set to the height of each sub-image.

This operation swaps the two major dimensions, so that page N in the output contains the Nth scanline, in order, from each input page.

You can override the VIPS_META_PAGE_HEIGHT metadata item with the optional page_height parameter.

VIPS_META_PAGE_HEIGHT in the output image is the number of pages in the input image.

See also: vips_grid().

[method]

vips_wrap ()

int
vips_wrap (VipsImage *in,
           VipsImage **out,
           ...);

Optional arguments:

Slice an image up and move the segments about so that the pixel that was at 0, 0 is now at x , y . If x and y are not set, they default to the centre of the image.

See also: vips_embed(), vips_replicate().

[method]

vips_rot ()

int
vips_rot (VipsImage *in,
          VipsImage **out,
          VipsAngle angle,
          ...);

Rotate in by a multiple of 90 degrees.

Use vips_similarity() to rotate by an arbitary angle. vips_rot45() is useful for rotating convolution masks by 45 degrees.

See also: vips_flip(), vips_similarity(), vips_rot45().

[method]

vips_rot90 ()

int
vips_rot90 (VipsImage *in,
            VipsImage **out,
            ...);

Rotate in by 90 degress clockwise. A convenience function over vips_rot().

See also: vips_rot().

vips_rot180 ()

int
vips_rot180 (VipsImage *in,
             VipsImage **out,
             ...);

Rotate in by 180 degress. A convenience function over vips_rot().

See also: vips_rot().

[method]

vips_rot270 ()

int
vips_rot270 (VipsImage *in,
             VipsImage **out,
             ...);

Rotate in by 270 degress clockwise. A convenience function over vips_rot().

See also: vips_rot().

[method]

vips_rot45 ()

int
vips_rot45 (VipsImage *in,
            VipsImage **out,
            ...);

Optional arguments:

Rotate in by a multiple of 45 degrees. Odd-length sides and square images only.

This operation is useful for rotating convolution masks. Use vips_similarity() to rotate images by arbitrary angles.

See also: vips_rot(), vips_similarity().

[method]

vips_autorot_get_angle ()

VipsAngle
vips_autorot_get_angle (VipsImage *image);

Examine the metadata on im and return the VipsAngle to rotate by to turn the image upright.

See also: vips_autorot().

vips_autorot_remove_angle ()

void
vips_autorot_remove_angle (VipsImage *image);

Remove the orientation tag on image . Also remove any exif orientation tags.

See also: vips_autorot_get_angle().

[method]

vips_autorot ()

int
vips_autorot (VipsImage *in,
              VipsImage **out,
              ...);

Optional arguments:

Look at the image metadata and rotate the image to make it upright. The VIPS_META_ORIENTATION tag is removed from out to prevent accidental double rotation.

Read angle to find the amount the image was rotated by.

vips only supports the four simple rotations, it does not support the various mirror modes. If the image is using one of these mirror modes, the image is not rotated and the VIPS_META_ORIENTATION tag is not removed.

See also: vips_autorot_get_angle(), vips_autorot_remove_angle(), vips_rot().

[method]

vips_zoom ()

int
vips_zoom (VipsImage *in,
           VipsImage **out,
           int xfac,
           int yfac,
           ...);

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

See also: vips_affine(), vips_subsample().

[method]

vips_subsample ()

int
vips_subsample (VipsImage *in,
                VipsImage **out,
                int xfac,
                int yfac,
                ...);

Optional arguments:

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

For small horizontal shrinks, this operation will fetch lines of pixels from in and then subsample that line. For large shrinks it will fetch single pixels.

If point is set, in will always be sampled in points. This can be faster if the previous operations in the pipeline are very slow.

See also: vips_affine(), vips_shrink(), vips_zoom().

[method]

vips_cast ()

int
vips_cast (VipsImage *in,
           VipsImage **out,
           VipsBandFormat format,
           ...);

Optional arguments:

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

Casting from complex to real returns the real part.

If shift is TRUE, integer values are shifted up and down. For example, casting from unsigned 8 bit to unsigned 16 bit would shift every value left by 8 bits. The bottom bit is copied into the new bits, so 255 would become 65535.

See also: vips_scale(), vips_complexform(), vips_real(), vips_imag(), vips_cast_uchar(), vips_msb().

[method]

vips_cast_uchar ()

int
vips_cast_uchar (VipsImage *in,
                 VipsImage **out,
                 ...);

Convert in to VIPS_FORMAT_UCHAR. See vips_cast().

[method]

vips_cast_char ()

int
vips_cast_char (VipsImage *in,
                VipsImage **out,
                ...);

Convert in to VIPS_FORMAT_CHAR. See vips_cast().

[method]

vips_cast_ushort ()

int
vips_cast_ushort (VipsImage *in,
                  VipsImage **out,
                  ...);

Convert in to VIPS_FORMAT_USHORT. See vips_cast().

[method]

vips_cast_short ()

int
vips_cast_short (VipsImage *in,
                 VipsImage **out,
                 ...);

Convert in to VIPS_FORMAT_SHORT. See vips_cast().

[method]

vips_cast_uint ()

int
vips_cast_uint (VipsImage *in,
                VipsImage **out,
                ...);

Convert in to VIPS_FORMAT_UINT. See vips_cast().

[method]

vips_cast_int ()

int
vips_cast_int (VipsImage *in,
               VipsImage **out,
               ...);

Convert in to VIPS_FORMAT_INT. See vips_cast().

[method]

vips_cast_float ()

int
vips_cast_float (VipsImage *in,
                 VipsImage **out,
                 ...);

Convert in to VIPS_FORMAT_FLOAT. See vips_cast().

[method]

vips_cast_double ()

int
vips_cast_double (VipsImage *in,
                  VipsImage **out,
                  ...);

Convert in to VIPS_FORMAT_DOUBLE. See vips_cast().

[method]

vips_cast_complex ()

int
vips_cast_complex (VipsImage *in,
                   VipsImage **out,
                   ...);

Convert in to VIPS_FORMAT_COMPLEX. See vips_cast().

[method]

vips_cast_dpcomplex ()

int
vips_cast_dpcomplex (VipsImage *in,
                     VipsImage **out,
                     ...);

Convert in to VIPS_FORMAT_DPCOMPLEX. See vips_cast().

[method]

vips_scale ()

int
vips_scale (VipsImage *in,
            VipsImage **out,
            ...);

Optional arguments:

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.

If log is set, transform with log10(1.0 + pow(x, exp )) + .5, then scale so max == 255. By default, exp is 0.25.

See also: vips_cast().

[method]

vips_msb ()

int
vips_msb (VipsImage *in,
          VipsImage **out,
          ...);

Optional arguments:

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.

Use band to make a one-band 8-bit image.

This operator also works for LABQ coding.

See also: vips_scale(), vips_cast().

[method]

vips_byteswap ()

int
vips_byteswap (VipsImage *in,
               VipsImage **out,
               ...);

Swap the byte order in an image.

See also: vips_rawload().

[method]

vips_bandjoin ()

int
vips_bandjoin (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

See also: vips_insert().

vips_bandjoin2 ()

int
vips_bandjoin2 (VipsImage *in1,
                VipsImage *in2,
                VipsImage **out,
                ...);

Join a pair of images together, bandwise. See vips_bandjoin().

vips_bandjoin_const ()

int
vips_bandjoin_const (VipsImage *in,
                     VipsImage **out,
                     double *c,
                     int n,
                     ...);

Append a set of constant bands to an image.

See also: vips_bandjoin().

[method]

vips_bandjoin_const1 ()

int
vips_bandjoin_const1 (VipsImage *in,
                      VipsImage **out,
                      double c,
                      ...);

Append a single constant band to an image.

[method]

vips_bandrank ()

int
vips_bandrank (VipsImage **in,
               VipsImage **out,
               int n,
               ...);

Optional arguments:

Sorts the images in band-element-wise, then outputs an image in which each band element is selected from the sorted list by the index parameter. For example, if index is zero, then each output band element will be the minimum of all the corresponding input band elements.

By default, index is -1, meaning pick the median value.

It works for any uncoded, non-complex image type. Images are cast up to the smallest common-format.

Any image can have either 1 band or n bands, where n is the same for all the non-1-band images. Single band images are then effectively copied to make n-band images.

Smaller input images are expanded by adding black pixels.

See also: vips_rank().

vips_bandfold ()

int
vips_bandfold (VipsImage *in,
               VipsImage **out,
               ...);

Optional arguments:

Fold up an image horizontally: width is collapsed into bands. Use factor to set how much to fold by: factor 3, for example, will make the output image three times narrower than the input, and with three times as many bands. By default the whole of the input width is folded up.

See also: vips_csvload(), vips_bandunfold().

[method]

vips_bandunfold ()

int
vips_bandunfold (VipsImage *in,
                 VipsImage **out,
                 ...);

Optional arguments:

Unfold image bands into x axis. Use factor to set how much to unfold by: factor 3, for example, will make the output image three times wider than the input, and with one third as many bands. By default, all bands are unfolded.

See also: vips_csvload(), vips_bandfold().

[method]

vips_bandbool ()

int
vips_bandbool (VipsImage *in,
               VipsImage **out,
               VipsOperationBoolean boolean,
               ...);

Perform various boolean operations across the bands of an image. For example, a three-band uchar image operated on with VIPS_OPERATION_BOOLEAN_AND will produce a one-band uchar image where each pixel is the bitwise and of the band elements of the corresponding pixel in the input image.

The output image is the same format as the input image for integer types. Float types are cast to int before processing. Complex types are not supported.

The output image always has one band.

This operation is useful in conjuction with vips_relational(). You can use it to see if all image bands match exactly.

See also: vips_boolean_const().

[method]

vips_bandand ()

int
vips_bandand (VipsImage *in,
              VipsImage **out,
              ...);

Perform VIPS_OPERATION_BOOLEAN_AND on an image. See vips_bandbool().

[method]

vips_bandor ()

int
vips_bandor (VipsImage *in,
             VipsImage **out,
             ...);

Perform VIPS_OPERATION_BOOLEAN_OR on an image. See vips_bandbool().

[method]

vips_bandeor ()

int
vips_bandeor (VipsImage *in,
              VipsImage **out,
              ...);

Perform VIPS_OPERATION_BOOLEAN_EOR on an image. See vips_bandbool().

[method]

vips_bandmean ()

int
vips_bandmean (VipsImage *in,
               VipsImage **out,
               ...);

This operation writes a one-band image where each pixel is the average of the bands for that pixel in the input image. The output band format is the same as the input band format. Integer types use round-to-nearest averaging.

See also: vips_add(), vips_avg(), vips_recomb()

[method]

vips_recomb ()

int
vips_recomb (VipsImage *in,
             VipsImage **out,
             VipsImage *m,
             ...);

This operation recombines an image's bands. Each pixel in in is treated as an n-element vector, where n is the number of bands in in , and multipled by the n x m matrix m to produce the m-band image out .

out is always float, unless in is double, in which case out is double too. No complex images allowed.

It's useful for various sorts of colour space conversions.

See also: vips_bandmean().

[method]

vips_ifthenelse ()

int
vips_ifthenelse (VipsImage *cond,
                 VipsImage *in1,
                 VipsImage *in2,
                 VipsImage **out,
                 ...);

Optional arguments:

This operation scans the condition image cond and uses it to select pixels from either the then image in1 or the else image in2 . Non-zero means in1 , 0 means in2 .

Any image can have either 1 band or n bands, where n is the same for all the non-1-band images. Single band images are then effectively copied to make n-band images.

Images in1 and in2 are cast up to the smallest common format. cond is cast to uchar.

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

If blend is TRUE, then values in out are smoothly blended between in1 and in2 using the formula:

out = (cond / 255) * in1 + (1 - cond / 255) * in2

See also: vips_equal().

vips_switch ()

int
vips_switch (VipsImage **tests,
             VipsImage **out,
             int n,
             ...);

The tests images are evaluated and at each point the index of the first non-zero value is written to out . If all tests are false, the value (n + 1) is written.

Images in tests must have one band. They are expanded to the bounding box of the set of images in tests , and that size is used for out . tests can have up to 255 elements.

Combine with vips_case() to make an efficient multi-way vips_ifthenelse().

See also: vips_maplut(), vips_case(), vips_ifthenelse().

[method]

vips_flatten ()

int
vips_flatten (VipsImage *in,
              VipsImage **out,
              ...);

Optional arguments:

Take the last band of in as an alpha and use it to blend the remaining channels with background .

The alpha channel is 0 - max_alpha , where 1 means 100% image and 0 means 100% background. Non-complex images only. background defaults to zero (black).

max_alpha has the default value 255, or 65535 for images tagged as VIPS_INTERPRETATION_RGB16 or VIPS_INTERPRETATION_GREY16.

Useful for flattening PNG images to RGB.

See also: vips_premultiply(), vips_pngload().

[method]

vips_addalpha ()

int
vips_addalpha (VipsImage *in,
               VipsImage **out,
               ...);

Append an alpha channel.

See also: vips_image_hasalpha().

[method]

vips_premultiply ()

int
vips_premultiply (VipsImage *in,
                  VipsImage **out,
                  ...);

Optional arguments:

Premultiplies any alpha channel. The final band is taken to be the alpha and the bands are transformed as:

1
2
3

alpha = clip( 0, in[in.bands - 1], @max_alpha ); 
norm = alpha / @max_alpha; 
out = [in[0] * norm, ..., in[in.bands - 1] * norm, alpha];

So for an N-band image, the first N - 1 bands are multiplied by the clipped and normalised final band, the final band is clipped. If there is only a single band, the image is passed through unaltered.

The result is VIPS_FORMAT_FLOAT unless the input format is VIPS_FORMAT_DOUBLE, in which case the output is double as well.

max_alpha has the default value 255, or 65535 for images tagged as VIPS_INTERPRETATION_RGB16 or VIPS_INTERPRETATION_GREY16.

Non-complex images only.

See also: vips_unpremultiply(), vips_flatten().

[method]

vips_unpremultiply ()

int
vips_unpremultiply (VipsImage *in,
                    VipsImage **out,
                    ...);

Optional arguments:

Unpremultiplies any alpha channel. Band alpha_band (by default the final band) contains the alpha and all other bands are transformed as:

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alpha = (int) clip( 0, in[in.bands - 1], @max_alpha ); 
norm = (double) alpha / @max_alpha; 
if( alpha == 0 )
	out = [0, ..., 0, alpha];
else
	out = [in[0] / norm, ..., in[in.bands - 1] / norm, alpha];

So for an N-band image, the first N - 1 bands are divided by the clipped and normalised final band, the final band is clipped. If there is only a single band, the image is passed through unaltered.

The result is VIPS_FORMAT_FLOAT unless the input format is VIPS_FORMAT_DOUBLE, in which case the output is double as well.

max_alpha has the default value 255, or 65535 for images tagged as VIPS_INTERPRETATION_RGB16 or VIPS_INTERPRETATION_GREY16.

Non-complex images only.

See also: vips_premultiply(), vips_flatten().

[method]

vips_composite ()

int
vips_composite (VipsImage **in,
                VipsImage **out,
                int n,
                int *mode,
                ...);

Optional arguments:

Composite an array of images together.

Images are placed in a stack, with in [0] at the bottom and in [n - 1] at the top. Pixels are blended together working from the bottom upwards, with the blend mode at each step being set by the corresponding VipsBlendMode in mode .

Images are transformed to a compositing space before processing. This is VIPS_INTERPRETATION_sRGB, VIPS_INTERPRETATION_B_W, VIPS_INTERPRETATION_RGB16, or VIPS_INTERPRETATION_GREY16 by default, depending on how many bands and bits the input images have. You can select any other space, such as VIPS_INTERPRETATION_LAB or VIPS_INTERPRETATION_scRGB.

The output image is in the compositing space. It will always be VIPS_FORMAT_FLOAT unless one of the inputs is VIPS_FORMAT_DOUBLE, in which case the output will be double as well.

Complex images are not supported.

The output image will always have an alpha band. A solid alpha is added to any input missing an alpha.

The images do not need to match in size or format. They will be expanded to the smallest common size and format in the usual way. Images are positioned using the x and y parameters, if set.

Image are normally treated as unpremultiplied, so this operation can be used directly on PNG images. If your images have been through vips_premultiply(), set premultiplied .

See also: vips_insert().

[method]

vips_composite2 ()

int
vips_composite2 (VipsImage *base,
                 VipsImage *overlay,
                 VipsImage **out,
                 VipsBlendMode mode1,
                 ...);

Optional arguments:

Composite overlay on top of base with mode . See vips_composite().

[method]

vips_falsecolour ()

int
vips_falsecolour (VipsImage *in,
                  VipsImage **out,
                  ...);

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

See also: vips_maplut().

[method]

vips_gamma ()

int
vips_gamma (VipsImage *in,
            VipsImage **out,
            ...);

Optional arguments:

Calculate in ** (1 / exponent ), normalising to the maximum range of the input type. For float types use 1.0 as the maximum.

See also: vips_identity(), vips_pow_const1(), vips_maplut()

[method]

enum VipsExtend

See vips_embed(), vips_conv(), vips_affine() and so on.

When the edges of an image are extended, you can specify how you want the extension done.

VIPS_EXTEND_BLACK --- new pixels are black, ie. all bits are zero.

VIPS_EXTEND_COPY --- each new pixel takes the value of the nearest edge pixel

VIPS_EXTEND_REPEAT --- the image is tiled to fill the new area

VIPS_EXTEND_MIRROR --- the image is reflected and tiled to reduce hash edges

VIPS_EXTEND_WHITE --- new pixels are white, ie. all bits are set

VIPS_EXTEND_BACKGROUND --- colour set from the background property

We have to specify the exact value of each enum member since we have to keep these frozen for back compat with vips7.

See also: vips_embed().

enum VipsCompassDirection

A direction on a compass. Used for vips_gravity(), for example.

enum VipsDirection

See vips_flip(), vips_join() and so on.

Operations like vips_flip() need to be told whether to flip left-right or top-bottom.

See also: vips_flip(), vips_join().

enum VipsAlign

See vips_join() and so on.

Operations like vips_join() need to be told whether to align images on the low or high coordinate edge, or centre.

See also: vips_join().

enum VipsAngle

See vips_rot() and so on.

Fixed rotate angles.

See also: vips_rot().

enum VipsAngle45

See vips_rot45() and so on.

Fixed rotate angles.

See also: vips_rot45().

enum VipsInteresting

Pick the algorithm vips uses to decide image "interestingness". This is used by vips_smartcrop(), for example, to decide what parts of the image to keep.

VIPS_INTERESTING_NONE and VIPS_INTERESTING_LOW mean the same -- the crop is positioned at the top or left. VIPS_INTERESTING_HIGH positions at the bottom or right.

See also: vips_smartcrop().

enum VipsBlendMode

The various Porter-Duff and PDF blend modes. See vips_composite(), for example.

The Cairo docs have a nice explanation of all the blend modes:

https://www.cairographics.org/operators

The non-separable modes are not implemented.