• VIPS_INTERPRETATION_LAB -- CIELAB '76 colourspace with a D65 white. This uses three floats for each band, and bands have the obvious range.

  There are two variants, VIPS_INTERPRETATION_LABQ and VIPS_INTERPRETATION_LABS, which use ints to store values. These are less precise, but can be quicker to store and process.

  VIPS_INTERPRETATION_LCH is the same, but with a*b* as polar coordinates. Hue is expressed in degrees.

• VIPS_INTERPRETATION_XYZ -- CIE XYZ. This uses three floats. See VIPS_D75_X0 and friends for values for the ranges under various illuminants.

  VIPS_INTERPRETATION_YXY is the same, but with little x and y.

• VIPS_INTERPRETATION_scRGB -- a linear colourspace with the sRGB primaries. This is useful if you need linear light and don't care much what the primaries are.

  Linearization is performed with the usual sRGB equations, see below.

• VIPS_INTERPRETATION_sRGB -- the standard sRGB colourspace, see: wikipedia sRGB.

  This uses three 8-bit values for each of RGB.

  VIPS_INTERPRETATION_RGB16 is the same, but using three 16-bit values for RGB.

  VIPS_INTERPRETATION_HSV is sRGB, but in polar coordinates. VIPS_INTERPRETATION_LCH is much better, only use HSV if you have to.

• VIPS_INTERPRETATION_B_W -- a monochrome image, roughly G from sRGB. The grey value is calculated in VIPS_INTERPRETATION_scRGB space with the usual 0.2, 0.7, 0.1 RGB ratios.

  VIPS_INTERPRETATION_GREY16 is the same, but using 16-bits.

• VIPS_INTERPRETATION_CMC -- a colour space based on the CMC(1:1) colour difference measurement. This is a highly uniform colour space, much better than CIELAB for expressing small differences.

  The CMC colourspace is described in "Uniform Colour Space Based on the CMC(l:c) Colour-difference Formula", M R Luo and B Rigg, Journal of the Society of Dyers and Colourists, vol 102, 1986. Distances in this colourspace approximate, within 10% or so, differences in the CMC(l:c) colour difference formula.

  You can calculate metrics like CMC(2:1) by scaling the spaces before finding differences.

vips_colourspace_issupported ()

gboolean
vips_colourspace_issupported (const VipsImage *image);

Test if image is in a colourspace that vips_colourspace() can process.

vips_colourspace ()

int
vips_colourspace (VipsImage *in,
 VipsImage **out,
 VipsInterpretation space,
 ...);

Optional arguments:

This operation looks at the interpretation field of in (or uses source_space , if set) and runs a set of colourspace conversion functions to move it to space .

For example, given an image tagged as VIPS_INTERPRETATION_YXY, running vips_colourspace() with space set to VIPS_INTERPRETATION_LAB will convert with vips_Yxy2XYZ() and vips_XYZ2Lab().

See also: vips_colourspace_issupported(), vips_image_guess_interpretation().

[method]

vips_LabQ2sRGB ()

int
vips_LabQ2sRGB (VipsImage *in,
 VipsImage **out,
 ...);

Unpack a LabQ (VIPS_CODING_LABQ) image to a three-band short image.

See also: vips_LabS2LabQ(), vips_LabQ2sRGB(), vips_rad2float().

[method]

vips_rad2float ()

int
vips_rad2float (VipsImage *in,
 VipsImage **out,
 ...);

Unpack a RAD (VIPS_CODING_RAD) image to a three-band float image.

See also: vips_float2rad(), vips_LabQ2LabS().

[method]

vips_float2rad ()

int
vips_float2rad (VipsImage *in,
 VipsImage **out,
 ...);

Convert a three-band float image to Radiance 32-bit packed format.

See also: vips_rad2float(), VIPS_CODING_RAD, vips_LabQ2Lab().

[method]

vips_LabS2LabQ ()

int
vips_LabS2LabQ (VipsImage *in,
 VipsImage **out,
 ...);

Convert a LabS three-band signed short image to LabQ

See also: vips_LabQ2LabS().

[method]

vips_LabQ2LabS ()

int
vips_LabQ2LabS (VipsImage *in,
 VipsImage **out,
 ...);

Unpack a LabQ (VIPS_CODING_LABQ) image to a three-band short image.

See also: vips_LabS2LabQ(), vips_LabQ2LabS(), vips_rad2float().

[method]

vips_LabQ2Lab ()

int
vips_LabQ2Lab (VipsImage *in,
 VipsImage **out,
 ...);

Unpack a LabQ (VIPS_CODING_LABQ) image to a three-band float image.

See also: vips_LabQ2Lab(), vips_LabQ2LabS(), vips_rad2float().

[method]

vips_Lab2LabQ ()

int
vips_Lab2LabQ (VipsImage *in,
 VipsImage **out,
 ...);

Convert a Lab three-band float image to LabQ (VIPS_CODING_LABQ).

See also: vips_LabQ2Lab().

[method]

vips_LCh2Lab ()

int
vips_LCh2Lab (VipsImage *in,
 VipsImage **out,
 ...);

Turn LCh to Lab.

[method]

vips_Lab2LCh ()

int
vips_Lab2LCh (VipsImage *in,
 VipsImage **out,
 ...);

Turn Lab to LCh.

[method]

vips_Yxy2Lab ()

int
vips_Yxy2Lab (VipsImage *in,
 VipsImage **out,
 ...);

vips_CMC2XYZ ()

int
vips_CMC2XYZ (VipsImage *in,
 VipsImage **out,
 ...);

vips_Lab2XYZ ()

int
vips_Lab2XYZ (VipsImage *in,
 VipsImage **out,
 ...);

Optional arguments:

Turn Lab to XYZ. The colour temperature defaults to D65, but can be specified with temp .

[method]

vips_XYZ2Lab ()

int
vips_XYZ2Lab (VipsImage *in,
 VipsImage **out,
 ...);

Optional arguments:

Turn XYZ to Lab, optionally specifying the colour temperature. temp defaults to D65.

[method]

vips_XYZ2scRGB ()

int
vips_XYZ2scRGB (VipsImage *in,
 VipsImage **out,
 ...);

Turn XYZ to scRGB.

[method]

vips_scRGB2sRGB ()

int
vips_scRGB2sRGB (VipsImage *in,
 VipsImage **out,
 ...);

Optional arguments:

Convert an scRGB image to sRGB. Set depth to 16 to get 16-bit output.

If depth is 16, any extra channels after RGB are multiplied by 256.

See also: vips_LabS2LabQ(), vips_sRGB2scRGB(), vips_rad2float().

[method]

vips_scRGB2BW ()

int
vips_scRGB2BW (VipsImage *in,
 VipsImage **out,
 ...);

Optional arguments:

Convert an scRGB image to greyscale. Set depth to 16 to get 16-bit output.

If depth is 16, any extra channels after RGB are multiplied by 256.

See also: vips_LabS2LabQ(), vips_sRGB2scRGB(), vips_rad2float().

[method]

vips_sRGB2scRGB ()

int
vips_sRGB2scRGB (VipsImage *in,
 VipsImage **out,
 ...);

Convert an sRGB image to scRGB. The input image can be 8 or 16-bit.

If the input image is tagged as VIPS_INTERPRETATION_RGB16, any extra channels after RGB are divided by 256. Thus, scRGB alpha is always 0 - 255.99.

See also: vips_scRGB2XYZ(), vips_scRGB2sRGB(), vips_rad2float().

[method]

vips_scRGB2XYZ ()

int
vips_scRGB2XYZ (VipsImage *in,
 VipsImage **out,
 ...);

Turn XYZ to scRGB.

[method]

vips_HSV2sRGB ()

int
vips_HSV2sRGB (VipsImage *in,
 VipsImage **out,
 ...);

Convert HSV to sRGB.

HSV is a crude polar coordinate system for RGB images. It is provided for compatibility with other image processing systems. See vips_Lab2LCh() for a much better colour space.

See also: vips_sRGB2HSV().

[method]

vips_sRGB2HSV ()

int
vips_sRGB2HSV (VipsImage *in,
 VipsImage **out,
 ...);

Convert to HSV.

HSV is a crude polar coordinate system for RGB images. It is provided for compatibility with other image processing systems. See vips_Lab2LCh() for a much better colour space.

See also: vips_HSV2sRGB(), vips_Lab2LCh().

[method]

vips_LCh2CMC ()

int
vips_LCh2CMC (VipsImage *in,
 VipsImage **out,
 ...);

Turn LCh to CMC.

The CMC colourspace is described in "Uniform Colour Space Based on the CMC(l:c) Colour-difference Formula", M R Luo and B Rigg, Journal of the Society of Dyers and Colourists, vol 102, 1986. Distances in this colourspace approximate, within 10% or so, differences in the CMC(l:c) colour difference formula.

This operation generates CMC(1:1). For CMC(2:1), halve Lucs and double Cucs.

See also: vips_CMC2LCh().

[method]

vips_CMC2LCh ()

int
vips_CMC2LCh (VipsImage *in,
 VipsImage **out,
 ...);

Turn LCh to CMC.

See also: vips_LCh2CMC().

[method]

vips_XYZ2Yxy ()

int
vips_XYZ2Yxy (VipsImage *in,
 VipsImage **out,
 ...);

Turn XYZ to Yxy.

[method]

vips_Yxy2XYZ ()

int
vips_Yxy2XYZ (VipsImage *in,
 VipsImage **out,
 ...);

Turn XYZ to Yxy.

[method]

vips_LabS2Lab ()

int
vips_LabS2Lab (VipsImage *in,
 VipsImage **out,
 ...);

Convert a LabS three-band signed short image to a three-band float image.

See also: vips_LabS2Lab().

[method]

vips_Lab2LabS ()

int
vips_Lab2LabS (VipsImage *in,
 VipsImage **out,
 ...);

Turn Lab to LabS, signed 16-bit int fixed point.

See also: vips_LabQ2Lab().

[method]

vips_CMYK2XYZ ()

int
vips_CMYK2XYZ (VipsImage *in,
 VipsImage **out,
 ...);

Turn CMYK to XYZ. If the image has an embedded ICC profile this will be used for the conversion. If there is no embedded profile, a generic fallback profile will be used.

Conversion is to D65 XYZ with relative intent. If you need more control over the process, use vips_icc_import() instead.

[method]

vips_XYZ2CMYK ()

int
vips_XYZ2CMYK (VipsImage *in,
 VipsImage **out,
 ...);

Turn XYZ to CMYK. If the image has an embedded ICC profile this will be used for the conversion. If there is no embedded profile, a generic fallback profile will be used.

Conversion is from D65 XYZ with relative intent. If you need more control over the process, use vips_icc_export() instead.

[method]

vips_profile_load ()

int
vips_profile_load (const char *name,
 VipsBlob **profile,
 ...);

Load a named profile.

Profiles are loaded from four sources:

vips_icc_present ()

int
vips_icc_present (void);

VIPS can optionally be built without the ICC library. Use this function to test for its availability.

vips_icc_transform ()

int
vips_icc_transform (VipsImage *in,
 VipsImage **out,
 const char *output_profile,
 ...);

Optional arguments:

Transform an image with a pair of ICC profiles. The input image is moved to profile-connection space with the input profile and then to the output space with the output profile.

If embedded is set, the input profile is taken from the input image metadata, if present. If there is no embedded profile, input_profile is used as a fall-back. You can test for the presence of an embedded profile with vips_image_get_typeof() with VIPS_META_ICC_NAME as an argument. This will return GType 0 if there is no profile.

If embedded is not set, the input profile is taken from input_profile . If input_profile is not supplied, the metadata profile, if any, is used as a fall-back.

If black_point_compensation is set, LCMS black point compensation is enabled.

The output image has the output profile attached to the VIPS_META_ICC_NAME field.

Use vips_icc_import() and vips_icc_export() to do either the first or second half of this operation in isolation.

[method]

vips_icc_import ()

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

Optional arguments:

Import an image from device space to D65 LAB with an ICC profile. If pcs is set to VIPS_PCS_XYZ, use CIE XYZ PCS instead.

If embedded is set, the input profile is taken from the input image metadata. If there is no embedded profile, input_profile_filename is used as a fall-back. You can test for the presence of an embedded profile with vips_image_get_typeof() with VIPS_META_ICC_NAME as an argument. This will return GType 0 if there is no profile.

If embedded is not set, the input profile is taken from input_profile . If input_profile is not supplied, the metadata profile, if any, is used as a fall-back.

If black_point_compensation is set, LCMS black point compensation is enabled.

[method]

vips_icc_export ()

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

Optional arguments:

Export an image from D65 LAB to device space with an ICC profile. If pcs is set to VIPS_PCS_XYZ, use CIE XYZ PCS instead. If output_profile is not set, use the embedded profile, if any. If output_profile is set, export with that and attach it to the output image.

If black_point_compensation is set, LCMS black point compensation is enabled.

[method]

vips_icc_ac2rc ()

int
vips_icc_ac2rc (VipsImage *in,
 VipsImage **out,
 const char *profile_filename);

Transform an image from absolute to relative colorimetry using the MediaWhitePoint stored in the ICC profile.

See also: vips_icc_transform(), vips_icc_import().

[method]

vips_icc_is_compatible_profile ()

gboolean
vips_icc_is_compatible_profile (VipsImage *image,
 const void *data,
 size_t data_length);

vips_dE76 ()

int
vips_dE76 (VipsImage *left,
 VipsImage *right,
 VipsImage **out,
 ...);

Calculate dE 76.

vips_dE00 ()

int
vips_dE00 (VipsImage *left,
 VipsImage *right,
 VipsImage **out,
 ...);

Calculate dE 00.

vips_dECMC ()

int
vips_dECMC (VipsImage *left,
 VipsImage *right,
 VipsImage **out,
 ...);

Calculate dE CMC. The input images are transformed to CMC colour space and the euclidean distance between corresponding pixels calculated.

To calculate a colour difference with values for (l:c) other than (1:1), transform the two source images to CMC yourself, scale the channels appropriately, and call this function.

See also: vips_colourspace()

vips_col_Lab2XYZ ()

void
vips_col_Lab2XYZ (float L,
 float a,
 float b,
 float *X,
 float *Y,
 float *Z);

Calculate XYZ from Lab, D65.

See also: vips_Lab2XYZ().

vips_col_XYZ2Lab ()

void
vips_col_XYZ2Lab (float X,
 float Y,
 float Z,
 float *L,
 float *a,
 float *b);

Calculate XYZ from Lab, D65.

See also: vips_XYZ2Lab().

vips_col_ab2h ()

double
vips_col_ab2h (double a,
 double b);

vips_col_ab2Ch ()

void
vips_col_ab2Ch (float a,
 float b,
 float *C,
 float *h);

vips_col_Ch2ab ()

void
vips_col_Ch2ab (float C,
 float h,
 float *a,
 float *b);

Calculate ab from Ch, h in degrees.

vips_col_L2Lcmc ()

float
vips_col_L2Lcmc (float L);

Calculate Lcmc from L.

vips_col_C2Ccmc ()

float
vips_col_C2Ccmc (float C);

Calculate Ccmc from C.

vips_col_Ch2hcmc ()

float
vips_col_Ch2hcmc (float C,
 float h);

Calculate hcmc from C and h.

vips_col_make_tables_CMC ()

void
vips_col_make_tables_CMC (void);

Make the lookup tables for cmc.

vips_col_Lcmc2L ()

float
vips_col_Lcmc2L (float Lcmc);

Calculate L from Lcmc using a table. Call vips_col_make_tables_CMC() at least once before using this function.

vips_col_Ccmc2C ()

float
vips_col_Ccmc2C (float Ccmc);

Calculate C from Ccmc using a table. Call vips_col_make_tables_CMC() at least once before using this function.

vips_col_Chcmc2h ()

float
vips_col_Chcmc2h (float C,
 float hcmc);

Calculate h from C and hcmc, using a table. Call vips_col_make_tables_CMC() at least once before using this function.

vips_col_sRGB2scRGB_8 ()

int
vips_col_sRGB2scRGB_8 (int r,
 int g,
 int b,
 float *R,
 float *G,
 float *B);

vips_col_sRGB2scRGB_16 ()

int
vips_col_sRGB2scRGB_16 (int r,
 int g,
 int b,
 float *R,
 float *G,
 float *B);

vips_col_sRGB2scRGB_8_noclip ()

int
vips_col_sRGB2scRGB_8_noclip (int r,
 int g,
 int b,
 float *R,
 float *G,
 float *B);

vips_col_sRGB2scRGB_16_noclip ()

int
vips_col_sRGB2scRGB_16_noclip (int r,
 int g,
 int b,
 float *R,
 float *G,
 float *B);

vips_col_scRGB2XYZ ()

int
vips_col_scRGB2XYZ (float R,
 float G,
 float B,
 float *X,
 float *Y,
 float *Z);

vips_col_XYZ2scRGB ()

int
vips_col_XYZ2scRGB (float X,
 float Y,
 float Z,
 float *R,
 float *G,
 float *B);

vips_col_scRGB2sRGB_8 ()

int
vips_col_scRGB2sRGB_8 (float R,
 float G,
 float B,
 int *r,
 int *g,
 int *b,
 int *og);

vips_col_scRGB2sRGB_16 ()

int
vips_col_scRGB2sRGB_16 (float R,
 float G,
 float B,
 int *r,
 int *g,
 int *b,
 int *og);

vips_col_scRGB2BW_16 ()

int
vips_col_scRGB2BW_16 (float R,
 float G,
 float B,
 int *g,
 int *og);

vips_col_scRGB2BW_8 ()

int
vips_col_scRGB2BW_8 (float R,
 float G,
 float B,
 int *g,
 int *og);

vips_pythagoras ()

float
vips_pythagoras (float L1,
 float a1,
 float b1,
 float L2,
 float a2,
 float b2);

Pythagorean distance between two points in colour space. Lab/XYZ/CMC etc.

vips_col_dE00 ()

float
vips_col_dE00 (float L1,
 float a1,
 float b1,
 float L2,
 float a2,
 float b2);

CIEDE2000, from:

Luo, Cui, Rigg, "The Development of the CIE 2000 Colour-Difference Formula: CIEDE2000", COLOR research and application, pp 340

VIPS_D93_X0

#define VIPS_D93_X0 (89.7400)

Areas under curves for D93, 2 degree observer.

VIPS_D93_Y0

#define VIPS_D93_Y0 (100.0)

VIPS_D93_Z0

#define VIPS_D93_Z0 (130.7700)

VIPS_D75_X0

#define VIPS_D75_X0 (94.9682)

Areas under curves for D75, 2 degree observer.

VIPS_D75_Y0

#define VIPS_D75_Y0 (100.0)

VIPS_D75_Z0

#define VIPS_D75_Z0 (122.5710)

VIPS_D65_X0

#define VIPS_D65_X0 (95.0470)

Areas under curves for D65, 2 degree observer.

VIPS_D65_Y0

#define VIPS_D65_Y0 (100.0)

VIPS_D65_Z0

#define VIPS_D65_Z0 (108.8827)

VIPS_D55_X0

#define VIPS_D55_X0 (95.6831)

Areas under curves for D55, 2 degree observer.

VIPS_D55_Y0

#define VIPS_D55_Y0 (100.0)

VIPS_D55_Z0

#define VIPS_D55_Z0 (92.0871)

VIPS_D50_X0

#define VIPS_D50_X0 (96.4250)

Areas under curves for D50, 2 degree observer.

VIPS_D50_Y0

#define VIPS_D50_Y0 (100.0)

VIPS_D50_Z0

#define VIPS_D50_Z0 (82.4680)

VIPS_A_X0

#define VIPS_A_X0 (109.8503)

Areas under curves for illuminant A (2856K), 2 degree observer.

VIPS_A_Y0

#define VIPS_A_Y0 (100.0)

VIPS_A_Z0

#define VIPS_A_Z0 (35.5849)

VIPS_B_X0

#define VIPS_B_X0 (99.0720)

Areas under curves for illuminant B (4874K), 2 degree observer.

VIPS_B_Y0

#define VIPS_B_Y0 (100.0)

VIPS_B_Z0

#define VIPS_B_Z0 (85.2230)

VIPS_C_X0

#define VIPS_C_X0 (98.0700)

Areas under curves for illuminant C (6774K), 2 degree observer.

VIPS_C_Y0

#define VIPS_C_Y0 (100.0)

VIPS_C_Z0

#define VIPS_C_Z0 (118.2300)

VIPS_E_X0

#define VIPS_E_X0 (100.0)

Areas under curves for equal energy illuminant E.

VIPS_E_Y0

#define VIPS_E_Y0 (100.0)

VIPS_E_Z0

#define VIPS_E_Z0 (100.0)

VIPS_D3250_X0

#define VIPS_D3250_X0 (105.6590)

Areas under curves for black body at 3250K, 2 degree observer.

VIPS_D3250_Y0

#define VIPS_D3250_Y0 (100.0)

VIPS_D3250_Z0

#define VIPS_D3250_Z0 (45.8501)

enum VipsIntent

The rendering intent. VIPS_INTENT_ABSOLUTE is best for scientific work, VIPS_INTENT_RELATIVE is usually best for accurate communication with other imaging libraries.

enum VipsPCS

Pick a Profile Connection Space for vips_icc_import() and vips_icc_export(). LAB is usually best, XYZ can be more convenient in some cases.