colour docs
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John Cupitt
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@ -77,10 +77,82 @@
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* @see_also: <link linkend="libvips-arithmetic">arithmetic</link>
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* @include: vips/vips.h
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*
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* These operators let you transform images between colour spaces, and move
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* images to and from device spaces.
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* These operators let you transform coordinates and images between colour
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* spaces, calculate colour differences, and move
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* to and from device spaces.
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*/
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/* Areas under curves for Dxx. 2 degree observer.
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*/
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/**
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* IM_D93_X0:
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*
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*
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* Areas under curves for D93, 2 degree observer.
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*/
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/**
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* IM_D75_X0:
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*
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* Areas under curves for D75, 2 degree observer.
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*/
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/**
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* IM_D65_X0:
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*
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* Areas under curves for D65, 2 degree observer.
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*/
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/**
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* IM_D55_X0:
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*
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* Areas under curves for D55, 2 degree observer.
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*/
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/**
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* IM_D50_X0:
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*
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* Areas under curves for D50, 2 degree observer.
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*/
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/**
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* IM_A_X0:
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*
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* Areas under curves for illuminant A (2856K), 2 degree observer.
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*/
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/**
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* IM_B_X0:
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*
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* Areas under curves for illuminant B (4874K), 2 degree observer.
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*/
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/**
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* IM_C_X0:
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*
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* Areas under curves for illuminant C (6774K), 2 degree observer.
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*/
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/**
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* IM_E_X0:
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*
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* Areas under curves for equal energy illuminant E.
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*/
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/**
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* IM_D3250_X0:
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*
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* Areas under curves for black body at 3250K, 2 degree observer.
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*/
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/**
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* im_colour_temperature:
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* @X0: Area under X
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* @Y0: Area under Y
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* @Z0: Area under Z
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*
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* Pass colour temperatures to various operations with one of these.
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*/
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/* Have the tables been made?
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@ -93,7 +165,14 @@ static float LI[ 1001 ];
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static float CI[ 3001 ];
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static float hI[ 101 ][ 361 ];
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/* Calculate Ch from ab, h in degrees.
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/**
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* im_col_ab2Ch:
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* @a: CIE a* value
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* @b: CIE b* value
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* @C: return Chroma
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* @h: return Hue angle (degrees)
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*
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* Calculate Ch from ab, h in degrees.
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*/
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void
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im_col_ab2Ch( float a, float b, float *C, float *h )
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@ -107,7 +186,14 @@ im_col_ab2Ch( float a, float b, float *C, float *h )
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*h = out[2];
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}
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/* Calculate ab from Ch, h in degrees.
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/**
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* im_col_Ch2ab:
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* @C: Chroma
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* @h: Hue angle (degrees)
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* @a: return CIE a* value
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* @b: return CIE b* value
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*
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* Calculate ab from Ch, h in degrees.
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*/
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void
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im_col_Ch2ab( float C, float h, float *a, float *b )
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@ -121,7 +207,18 @@ im_col_Ch2ab( float C, float h, float *a, float *b )
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*b = out[2];
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}
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/* Calculate Lab from XYZ.
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/**
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* im_col_XYZ2Lab:
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* @X: Input CIE XYZ colour
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* @Y:
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* @Z:
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* @L: return CIE Lab value
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* @a:
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* @b:
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*
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* Calculate Lab from XYZ, D65.
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*
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* See also: im_XYZ2Lab_temp().
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*/
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void
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im_col_XYZ2Lab( float X, float Y, float Z, float *L, float *a, float *b )
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@ -141,7 +238,18 @@ im_col_XYZ2Lab( float X, float Y, float Z, float *L, float *a, float *b )
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*b = out[2];
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}
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/* Calculate XYZ from Lab.
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/**
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* im_col_Lab2XYZ:
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* @L: Input CIE Lab value
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* @a:
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* @b:
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* @X: Return CIE XYZ colour
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* @Y:
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* @Z:
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*
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* Calculate XYZ from Lab, D65.
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*
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* See also: im_Lab2XYZ_temp().
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*/
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void
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im_col_Lab2XYZ( float L, float a, float b, float *X, float *Y, float *Z )
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@ -161,7 +269,16 @@ im_col_Lab2XYZ( float L, float a, float b, float *X, float *Y, float *Z )
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*Z = out[2];
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}
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/* Pythagorean distance between two points in colour space. Lab/XYZ/UCS etc.
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/**
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* im_col_pythagoras:
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* @L1: Input coordinate 1
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* @a1:
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* @b1:
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* @L2: Input coordinate 2
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* @a2:
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* @b2:
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*
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* Pythagorean distance between two points in colour space. Lab/XYZ/UCS etc.
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*/
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float
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im_col_pythagoras( float L1, float a1, float b1, float L2, float a2, float b2 )
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@ -182,7 +299,13 @@ im_col_pythagoras( float L1, float a1, float b1, float L2, float a2, float b2 )
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#define c2 0.3838
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#define c3 38.54
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/* Calculate Lucs from L.
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/**
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* im_col_L2Lucs:
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* @L: CIE L*
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*
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* Calculate Lucs from L.
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*
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* Returns: Lucs
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*/
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float
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im_col_L2Lucs( float L )
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@ -221,8 +344,14 @@ make_LI( void )
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}
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}
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/* Inverse of above using table.
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/**
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* im_col_Lucs2L:
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* @L: L ucs
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*
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* Calculate L from Lucs using a table. Call im_col_make_tables_UCS() at
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* least once before using this function.
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*
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* Returns: L*
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*/
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float
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im_col_Lucs2L( float Lucs )
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@ -246,7 +375,13 @@ im_col_Lucs2L( float Lucs )
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#define c7 0.07216
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#define c8 4.907
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/* Calculate Cucs from C.
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/**
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* im_col_C2Cucs:
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* @C: Chroma
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*
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* Calculate Cucs from C.
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*
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* Returns: Cucs.
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*/
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float
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im_col_C2Cucs( float C )
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@ -284,7 +419,15 @@ make_CI( void )
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}
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/* Inverse of above using table.
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/**
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* im_col_Cucs2C:
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* @Cucs: Cucs
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*
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* Calculate C from Cucs using a table.
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* Call im_col_make_tables_UCS() at
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* least once before using this function.
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*
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* Returns: C.
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*/
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float
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im_col_Cucs2C( float Cucs )
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@ -300,7 +443,14 @@ im_col_Cucs2C( float Cucs )
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return( CI[known] + (CI[known+1]-CI[known])*(Cucs*10.0-known) );
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}
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/* Calculate hucs from h and C.
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/**
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* im_col_Ch2hucs:
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* @C: Chroma
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* @h: Hue (degrees)
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*
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* Calculate hucs from C and h.
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*
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* Returns: hucs.
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*/
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float
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im_col_Ch2hucs( float C, float h )
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@ -412,7 +562,16 @@ make_hI( void )
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}
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}
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/* Inverse of above, using table.
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/**
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* im_col_Chucs2h:
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* @C: Chroma
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* @hucs: Hue ucs (degrees)
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*
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* Calculate h from C and hucs, using a table.
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* Call im_col_make_tables_UCS() at
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* least once before using this function.
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*
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* Returns: h.
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*/
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float
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im_col_Chucs2h( float C, float hucs )
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@ -437,7 +596,10 @@ im_col_Chucs2h( float C, float hucs )
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(hI[r][(known + 1) % 360] - hI[r][known]) * (hucs - known) );
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}
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/* Make the lookup tables for ucs.
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/**
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* im_col_make_tables_UCS:
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*
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* Make the lookup tables for ucs.
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*/
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void
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im_col_make_tables_UCS( void )
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@ -450,7 +612,16 @@ im_col_make_tables_UCS( void )
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}
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}
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/* CMC colour difference using the above.
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/**
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* im_col_dECMC:
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* @L1: Input coordinate 1
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* @a1:
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* @b1:
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* @L2: Input coordinate 2
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* @a2:
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* @b2:
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*
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* CMC colour difference from a pair of Lab values.
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*/
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float
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im_col_dECMC( float L1, float a1, float b1,
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@ -488,7 +659,12 @@ im_col_dECMC( float L1, float a1, float b1,
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return( im_col_pythagoras( Lucs1, aucs1, bucs1, Lucs2, aucs2, bucs2 ) );
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}
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/* Find h in degrees from a/b.
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/**
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* im_col_ab2h:
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* @a: CIE a
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* @b: CIE b
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*
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* Returns: Hue (degrees)
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*/
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double
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im_col_ab2h( double a, double b )
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@ -520,11 +696,21 @@ im_col_ab2h( double a, double b )
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return( h );
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}
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/* CIEDE2000 ... from
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Luo, Cui, Rigg, "The Development of the CIE 2000 Colour-Difference
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Formula: CIEDE2000", COLOR research and application, pp 340
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/**
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* im_col_dE00:
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* @L1: Input coordinate 1
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* @a1:
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* @b1:
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* @L2: Input coordinate 2
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* @a2:
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* @b2:
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*
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* CIEDE2000, from:
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*
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* Luo, Cui, Rigg, "The Development of the CIE 2000 Colour-Difference
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* Formula: CIEDE2000", COLOR research and application, pp 340
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*
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* Returns: CIE dE2000 colour difference.
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*/
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float
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im_col_dE00( float L1, float a1, float b1,
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@ -117,8 +117,10 @@ float im_col_Ch2hucs( float C, float h );
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float im_col_Chucs2h( float C, float hucs );
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double im_col_ab2h( double a, double b );
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float im_col_dECMC( float, float, float, float, float, float );
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float im_col_dE00( float, float, float, float, float, float );
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float im_col_dECMC(
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float L1, float a1, float b1, float L2, float a2, float b2 );
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float im_col_dE00(
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float L1, float a1, float b1, float L2, float a2, float b2 );
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int im_Lab2LCh( IMAGE *, IMAGE * );
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int im_LCh2Lab( IMAGE *, IMAGE * );
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