Reland: [qcms] Fix build_output_lut to return correct data for parametric curves

third_party/qcms/src/transform_util.c

 //  qcms
 //  Copyright (C) 2009 Mozilla Foundation
 //
 // Permission is hereby granted, free of charge, to any person obtaining
 // a copy of this software and associated documentation files (the "Software"),
 // to deal in the Software without restriction, including without limitation
 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
 // and/or sell copies of the Software, and to permit persons to whom the Software
 // is furnished to do so, subject to the following conditions:
 //
@@ skipping 589 matching lines @@
                 float gamma_table[256];
                 uint16_t i;
                 uint16_t *output = malloc(sizeof(uint16_t)*256);
 
                 if (!output) {
                         *output_gamma_lut = NULL;
                         return;
                 }
 
                 compute_curve_gamma_table_type_parametric(gamma_table, trc->parameter, trc->count);
                 *output_gamma_lut_length = 256;

[Noel Gordon, 2016/04/21 06:01:54]

This line needs to be made more obvious.  Perhaps place it after the for loop
and somehow make it better refer to inverted_size, since that is the value that
is eventually stored there, right?

Maybe *output_gamma_lut_length = inverted_size near line 628 diff-right would
makes the code a lot clearer?

[radu.velea, 2016/04/21 07:13:45]

Done.

                 for(i = 0; i < 256; i++) {
                         output[i] = (uint16_t)(gamma_table[i] * 65535);
                 }
-                *output_gamma_lut = output;
+
+                uint16_t *inverted;
+                int inverted_size = 256;

[Noel Gordon, 2016/04/21 06:01:54]

These two variables need to be declared just after line 602 diff-right.

[radu.velea, 2016/04/21 07:13:45]

Done.

+
+                //XXX: the choice of a minimum of 256 here is not backed by any theory,
+                //     measurement or data, however it is what lcms uses.
+                //     the maximum number we would need is 65535 because that's the
+                //     accuracy used for computing the pre cache table
+                if (inverted_size < 256)
+                        inverted_size = 256;
+
+                inverted = invert_lut(output, 256, inverted_size);
+                if (!inverted)
+                        return;
+                *output_gamma_lut = inverted;
+                free(output);
         } else {
                 if (trc->count == 0) {
                         *output_gamma_lut = build_linear_table(4096);
                         *output_gamma_lut_length = 4096;
                 } else if (trc->count == 1) {
                         float gamma = 1./u8Fixed8Number_to_float(trc->data[0]);
                         *output_gamma_lut = build_pow_table(gamma, 4096);
                         *output_gamma_lut_length = 4096;
                 } else {
                         //XXX: the choice of a minimum of 256 here is not backed by any theory, 
                         //     measurement or data, however it is what lcms uses.
                         *output_gamma_lut_length = trc->count;
                         if (*output_gamma_lut_length < 256)
                                 *output_gamma_lut_length = 256;
 
                         *output_gamma_lut = invert_lut(trc->data, trc->count, *output_gamma_lut_length);
                 }
         }
 
 }