colour: use cmsFLAGS_NOOPTIMIZE to keep all precision

Author: kleisauke

libvips/colour/icc_transform.c

@@ -438,8 +438,9 @@ vips_icc_build( VipsObject *object )
 
 	/* Use cmsFLAGS_NOCACHE to disable the 1-pixel cache and make
 	 * calling cmsDoTransform() from multiple threads safe.
+	 * Use cmsFLAGS_NOOPTIMIZE to ensure we keep all precision.
 	 */
-	flags = cmsFLAGS_NOCACHE;
+	flags = cmsFLAGS_NOCACHE | cmsFLAGS_NOOPTIMIZE;
 
 	if( icc->black_point_compensation ) 
 		flags |= cmsFLAGS_BLACKPOINTCOMPENSATION;
@@ -773,7 +774,7 @@ vips_icc_import_build( VipsObject *object )
 
 	if( icc->pcs == VIPS_PCS_LAB ) { 
 		cmsCIExyY white;
-		cmsWhitePointFromTemp( &white, 6500 );
+		cmsWhitePointFromTemp( &white, 6504 );
 
 		icc->out_profile = cmsCreateLab4Profile( &white );
 	}
@@ -808,6 +809,13 @@ decode_lab( guint16 *fixed, float *lab, int n )
 	int i;
 
         for( i = 0; i < n; i++ ) {
+				/*cmsCIELab Lab;
+				cmsLabEncoded2FloatV2(&Lab, fixed);
+
+				lab[0] = (float) Lab.L;
+				lab[1] = (float) Lab.a;
+				lab[2] = (float) Lab.b;*/
+
                 lab[0] = (double) fixed[0] / 652.800;
                 lab[1] = ((double) fixed[1] / 256.0) - 128.0;
                 lab[2] = ((double) fixed[2] / 256.0) - 128.0;
@@ -827,6 +835,13 @@ decode_xyz( guint16 *fixed, float *xyz, int n )
 	int i;
 
         for( i = 0; i < n; i++ ) {
+				/*cmsCIEXYZ XYZ;
+				cmsXYZEncoded2Float(&XYZ, fixed);
+
+                xyz[0] = XYZ.X * 100;
+                xyz[1] = XYZ.Y * 100;
+                xyz[2] = XYZ.Z * 100;*/
+
                 xyz[0] = (double) fixed[0] / X_FAC;
                 xyz[1] = (double) fixed[1] / Y_FAC;
                 xyz[2] = (double) fixed[2] / Z_FAC;
@@ -936,7 +951,7 @@ vips_icc_export_build( VipsObject *object )
 
 	if( icc->pcs == VIPS_PCS_LAB ) { 
 		cmsCIExyY white;
-		cmsWhitePointFromTemp( &white, 6500 );
+		cmsWhitePointFromTemp( &white, 6504 );
 
 		icc->in_profile = cmsCreateLab4Profile( &white );
 	}
@@ -977,6 +992,9 @@ encode_lab( float *lab, guint16 *fixed, int n )
 	int i;
 
 	for( i = 0; i < n; i++ ) {
+		/*cmsCIELab Lab = {.L = lab[0], .a = lab[1], .b = lab[2]};
+		cmsFloat2LabEncodedV2(fixed, &Lab);*/
+
 		float L = lab[0];
 		float a = lab[1];
 		float b = lab[2];
@@ -1014,6 +1032,9 @@ encode_xyz( float *xyz, guint16 *fixed, int n )
 	int i;
 
 	for( i = 0; i < n; i++ ) {
+		/*cmsCIEXYZ XYZ = {.X = xyz[0], .Y = xyz[1], .Z = xyz[2]};
+		cmsFloat2XYZEncoded(fixed, &XYZ);*/
+
 		float X = xyz[0];
 		float Y = xyz[1];
 		float Z = xyz[2];
@@ -1228,7 +1249,7 @@ vips_icc_transform_init( VipsIccTransform *transform )
  * @out: (out): output image
  * @profile_filename: use this profile
  *
- * Transform an image from absolute to relative colorimetry using the
+ * Transform an image from absolute to relative colorimetric using the
  * MediaWhitePoint stored in the ICC profile.
  *
  * See also: vips_icc_transform(), vips_icc_import().

test/test-suite/test_resample.py

@@ -237,7 +237,6 @@ def test_thumbnail_icc(self):
         assert im.width == 290
         assert im.height == 442
         assert im.bands == 3
-        assert im.bands == 3
 
         # the colour distance should not deviate too much
         # (i.e. the embedded profile should not be ignored)