faster and more accurate sRGB <-> XYZ
just use one table, since all colour channels are the same now have more points in the float -> int direction, fewer in int -> float faster out of range detection
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John Cupitt
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a2d4c15049
commit
63a06e5f81
@ -7,6 +7,7 @@
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im_dECMC_fromLab(), im_dE00_from_Lab()
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as classes
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- added vips_colour_convert(), replaces all derived conversions
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- faster and more accurate sRGB <-> XYZ conversion
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- dzsave can write zoomify and google maps layout as well
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- tilecache supports threaded access
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- openslide2vips gets underlying tile size from openslide
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9
TODO
9
TODO
@ -1,11 +1,10 @@
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- see vips_col_sRGB2XYZ()
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t_r2Yr[] is a 1501 element array, but we just index with a uchar
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trim this down!
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- add something to dzsave to control pyramid depth ... can then use it for
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straight tiling
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- add mono as a colourspace? also rad?
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- rename INTERPRETATION_UCS to _CMC
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- something to test if an image is in a supported colourspace?
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at the moment we only look at interpretation, but for things like labq
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@ -10,6 +10,8 @@
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* 21/9/12
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* - redone as a class
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* - sRGB only, support for other RGBs is now via lcms
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* 1/11/12
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* - faster and more accurate sRGB <-> XYZ conversion
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*/
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/*
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@ -51,6 +53,8 @@
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#include "colour.h"
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#define TABLE_SIZE (20000)
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typedef VipsColourCode VipsLabQ2sRGB;
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typedef VipsColourCodeClass VipsLabQ2sRGBClass;
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@ -88,16 +92,11 @@ struct im_col_display {
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*/
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struct im_col_tab_disp {
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/*< private >*/
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float t_Yr2r[1501]; /* Conversion of Yr to r */
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float t_Yg2g[1501]; /* Conversion of Yg to g */
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float t_Yb2b[1501]; /* Conversion of Yb to b */
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float t_r2Yr[1501]; /* Conversion of r to Yr */
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float t_g2Yg[1501]; /* Conversion of g to Yg */
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float t_b2Yb[1501]; /* Conversion of b to Yb */
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float t_Y2v[TABLE_SIZE]; /* Conversion of Y to v */
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float t_v2Y[256]; /* Conversion of v to Y */
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float mat_XYZ2lum[3][3]; /* XYZ to Yr, Yg, Yb matrix */
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float mat_lum2XYZ[3][3]; /* Yr, Yg, Yb to XYZ matrix */
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float rstep, gstep, bstep;
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float ristep, gistep, bistep;
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float rstep; /* Scale Y by this to fit TABLE_SIZE */
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};
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/* Do our own indexing of the arrays below to make sure we get efficient mults.
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@ -140,7 +139,6 @@ calcul_tables( void *client )
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int i, j;
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float a, ga_i, ga, c, f, yo, p;
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float maxr, maxg, maxb;
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double **temp;
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c = (d->d_B - 100.0) / 500.0;
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@ -153,54 +151,13 @@ calcul_tables( void *client )
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p = d->d_P / 100.0;
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f = d->d_Vrwr / p;
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maxr = (float) d->d_Vrwr;
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table->ristep = maxr / 1500.0;
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table->rstep = a / 1500.0;
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table->rstep = a / (TABLE_SIZE - 1);
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for( i = 0; i < 1501; i++ )
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table->t_Yr2r[i] = f * (pow( i * table->rstep / a, ga_i ) - c);
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for( i = 0; i < TABLE_SIZE; i++ )
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table->t_Y2v[i] = f * (pow( i * table->rstep / a, ga_i ) - c);
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for( i = 0; i < 1501; i++ )
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table->t_r2Yr[i] = yo +
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a * pow( i * table->ristep / f + c, ga );
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/**** Green ****/
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yo = d->d_Y0G;
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a = d->d_YCG - yo;
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ga = d->d_gammaG;
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ga_i = 1.0 / ga;
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p = d->d_P / 100.0;
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f = d->d_Vrwg / p;
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maxg = (float)d->d_Vrwg;
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table->gistep = maxg / 1500.0;
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table->gstep = a / 1500.0;
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for( i = 0; i < 1501; i++ )
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table->t_Yg2g[i] = f * (pow( i * table->gstep / a, ga_i ) - c);
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for( i = 0; i < 1501; i++ )
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table->t_g2Yg[i] = yo +
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a * pow( i * table->gistep / f + c, ga );
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/**** Blue ****/
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yo = d->d_Y0B;
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a = d->d_YCB - yo;
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ga = d->d_gammaB;
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ga_i = 1.0 / ga;
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p = d->d_P / 100.0;
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f = d->d_Vrwb / p;
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maxb = (float)d->d_Vrwb;
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table->bistep = maxb / 1500.0;
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table->bstep = a / 1500.0;
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for( i = 0; i < 1501; i++ )
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table->t_Yb2b[i] = f * (pow( i * table->bstep / a, ga_i ) - c);
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for( i = 0; i < 1501; i++ )
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table->t_b2Yb[i] = yo +
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a * pow( i * table->bistep / f + c, ga );
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for( i = 0; i < 256; i++ )
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table->t_v2Y[i] = yo + a * pow( i / f + c, ga );
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if( !(temp = im_dmat_alloc( 0, 2, 0, 2 )) )
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return( NULL );
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@ -256,18 +213,14 @@ vips_col_sRGB2XYZ( int r, int g, int b, float *X, float *Y, float *Z )
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float Yr, Yg, Yb;
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int i;
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r = VIPS_CLIP( 0, r, 255 );
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g = VIPS_CLIP( 0, g, 255 );
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b = VIPS_CLIP( 0, b, 255 );
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i = VIPS_CLIP( 0, r, 255 );
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Yr = table->t_v2Y[i];
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i = r / table->ristep;
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Yr = table->t_r2Yr[i];
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i = VIPS_CLIP( 0, g, 255 );
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Yg = table->t_v2Y[i];
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i = g / table->gistep;
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Yg = table->t_g2Yg[i];
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i = b / table->bistep;
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Yb = table->t_b2Yb[i];
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i = VIPS_CLIP( 0, b, 255 );
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Yb = table->t_v2Y[i];
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*X = mat[0] * Yr + mat[1] * Yg + mat[2] * Yb;
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*Y = mat[3] * Yr + mat[4] * Yg + mat[5] * Yb;
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@ -300,35 +253,33 @@ vips_col_XYZ2sRGB( float X, float Y, float Z,
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Yg = mat[3] * X + mat[4] * Y + mat[5] * Z;
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Yb = mat[6] * X + mat[7] * Y + mat[8] * Z;
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/* Any negatives? If yes, set the out-of-range flag and bump up.
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/* Clip range, set the out-of-range flag.
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*/
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if( Yr < d->d_Y0R ) {
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or = 1;
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Yr = d->d_Y0R;
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}
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if( Yg < d->d_Y0G ) {
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or = 1;
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Yg = d->d_Y0G;
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}
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if( Yb < d->d_Y0B ) {
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or = 1;
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Yb = d->d_Y0B;
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}
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#define CLIP( L, V, H ) { \
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if( (V) < (L) ) { \
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(V) = (L); \
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or = 1; \
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} \
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if( (V) > (H) ) { \
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(V) = (H); \
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or = 1; \
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} \
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}
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/* Work out colour value (0-Vrw) to feed the tube to get that
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* luminosity.
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*/
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Yint = (Yr - d->d_Y0R) / table->rstep;
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Yint = VIPS_CLIP( 0, Yint, 1500 );
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r = IM_RINT( table->t_Yr2r[Yint] );
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CLIP( 0, Yint, TABLE_SIZE - 1);
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r = VIPS_RINT( table->t_Y2v[Yint] );
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Yint = (Yg - d->d_Y0G) / table->gstep;
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Yint = VIPS_CLIP( 0, Yint, 1500 );
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g = IM_RINT( table->t_Yg2g[Yint] );
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Yint = (Yg - d->d_Y0G) / table->rstep;
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CLIP( 0, Yint, TABLE_SIZE - 1);
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g = VIPS_RINT( table->t_Y2v[Yint] );
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Yint = (Yb - d->d_Y0B) / table->bstep;
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Yint = VIPS_CLIP( 0, Yint, 1500 );
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b = IM_RINT( table->t_Yb2b[Yint] );
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Yint = (Yb - d->d_Y0B) / table->rstep;
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CLIP( 0, Yint, TABLE_SIZE - 1);
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b = VIPS_RINT( table->t_Y2v[Yint] );
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*r_ret = r;
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*g_ret = g;
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@ -468,9 +419,9 @@ vips_LabQ2sRGB_init( VipsLabQ2sRGB *LabQ2sRGB )
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* @in: input image
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* @out: output image
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*
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* Unpack a LabQ (#IM_CODING_LABQ) image to a three-band short image.
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* Unpack a LabQ (#VIPS_CODING_LABQ) image to a three-band short image.
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*
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* See also: im_LabS2LabQ(), im_LabQ2sRGB(), im_rad2float().
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* See also: vips_LabS2LabQ(), vips_LabQ2sRGB(), vips_rad2float().
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*
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* Returns: 0 on success, -1 on error.
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*/
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