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

third_party/qcms/src/transform_util.c

Index: third_party/qcms/src/transform_util.c
diff --git a/third_party/qcms/src/transform_util.c b/third_party/qcms/src/transform_util.c
index fc19b650f4013400ce1239dd5e974c005afca80e..3d84716ed553a5db9205bf560d03dfa4f0f64b1c 100644
--- a/third_party/qcms/src/transform_util.c
+++ b/third_party/qcms/src/transform_util.c
@@ -600,6 +600,8 @@ void build_output_lut(struct curveType *trc,
                 float gamma_table[256];
                 uint16_t i;
                 uint16_t *output = malloc(sizeof(uint16_t)*256);
+                uint16_t *inverted;
+                int inverted_size = 256;
 
                 if (!output) {
                         *output_gamma_lut = NULL;
@@ -607,11 +609,24 @@ void build_output_lut(struct curveType *trc,
                 }
 
                 compute_curve_gamma_table_type_parametric(gamma_table, trc->parameter, trc->count);
-                *output_gamma_lut_length = 256;
+
                 for(i = 0; i < 256; i++) {
                         output[i] = (uint16_t)(gamma_table[i] * 65535);
                 }
-                *output_gamma_lut = output;
+
+                //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;
+                *output_gamma_lut_length = inverted_size;
+                free(output);
         } else {
                 if (trc->count == 0) {
                         *output_gamma_lut = build_linear_table(4096);