[qcms] Make build_output_lut output 4096 points for parametric curves

third_party/qcms/src/tests/qcms_test_output_trc.c

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the Chromium LICENSE file.
 
 #include "qcms.h"
 #include "qcms_test_util.h"
 
 #include <assert.h>
 #include <math.h>
 #include <stdio.h>
@@ skipping 21 matching lines @@
     sRGB = qcms_profile_sRGB();
 
     transform = qcms_transform_create(sRGB, QCMS_DATA_RGBA_8, target, QCMS_DATA_RGBA_8, QCMS_INTENT_DEFAULT);
     if (!transform) {
         fprintf(stderr, "Failed to create colour transform\n");
         qcms_profile_release(sRGB);
         qcms_profile_release(target);
         return EXIT_FAILURE;
     }
 
     *size = qcms_transform_get_output_trc_rgba(transform, target, QCMS_TRC_USHORT, NULL);

[Noel Gordon, 2016/04/28 07:30:27]

Good, now optional: should we assert(*size >= 256) here now?

[radu.velea, 2016/04/28 08:17:25]

I guess it couldn't hurt.

-    assert(*size == 256);
 
     *table = malloc(*size * sizeof(uint16_t) * 4);
     qcms_transform_get_output_trc_rgba(transform, target, QCMS_TRC_USHORT, *table);
 
     qcms_transform_release(transform);
     qcms_profile_release(sRGB);
     qcms_profile_release(target);
 
     return 0;
 }
@@ skipping 13 matching lines @@
     sRGB = qcms_profile_sRGB();
 
     transform = qcms_transform_create(source, QCMS_DATA_RGBA_8, sRGB, QCMS_DATA_RGBA_8, QCMS_INTENT_DEFAULT);
     if (!transform) {
         fprintf(stderr, "Failed to create colour transform\n");
         qcms_profile_release(sRGB);
         qcms_profile_release(source);
         return EXIT_FAILURE;
     }
 
     *size = qcms_transform_get_input_trc_rgba(transform, source, QCMS_TRC_USHORT, NULL);

[Noel Gordon, 2016/04/28 07:30:27]

Good, now optional: should we assert(*size >= 256) here now?

[radu.velea, 2016/04/28 08:17:25]

Done.

-    assert(*size == 256);
 
     *table = calloc(*size, sizeof(uint16_t) * 4);
     qcms_transform_get_input_trc_rgba(transform, source, QCMS_TRC_USHORT, *table);
 
     qcms_transform_release(transform);
     qcms_profile_release(sRGB);
     qcms_profile_release(source);
 
     return 0;
 }
 
 static int qcms_test_output_trc(size_t width,
         size_t height,
         int iterations,
         const char *in_path,
         const char *out_path,
         const int force_software)
 {
     qcms_profile *profile;
     uint16_t *gamma_table_out;
-    size_t gamma_table_size;
+    size_t output_size;
     size_t i;
 
     printf("Test qcms output gamma curve table integrity.\n");
 
     if (!in_path) {
         fprintf(stderr, "%s: please provide valid ICC profiles via -i option\n", __FUNCTION__);
         return EXIT_FAILURE;
     }
 
     // Create profiles and transforms, get table and then free resources to make sure none
     // of the internal tables are initialized by previous calls.
     gamma_table_out = NULL;
-    gamma_table_size = 0;
-    if (get_output_gamma_table(in_path, &gamma_table_out, &gamma_table_size) != 0) {
+    output_size = 0;
+    if (get_output_gamma_table(in_path, &gamma_table_out, &output_size) != 0) {
         fprintf(stderr, "Unable to extract output gamma table\n");
         return EXIT_FAILURE;
     }
 
-    printf("LUT size = %zu\n", gamma_table_size);
+    printf("LUT size = %zu\n", output_size);
 
     profile = qcms_profile_from_path(in_path);
     if (!profile) {
         fprintf(stderr, "Invalid input profile\n");
         free(gamma_table_out);
         return EXIT_FAILURE;
     }
 
     // Check only for red curve for now.
     if (profile->redTRC->type == PARAMETRIC_CURVE_TYPE) {
         int type = - (int)(profile->redTRC->count + 1);
+        uint16_t *gamma_table_in = NULL;
+        size_t input_size = 0;
+        float scale_factor;
         FILE *gamma_file;

[Noel Gordon, 2016/04/28 07:30:27]

gamma_file -> output_file.

[radu.velea, 2016/04/28 08:17:25]

Done.

-        uint16_t *gamma_table_in = NULL;
-        uint16_t *p_table_out, *p_table_in;
-        char file_name[256] = {0,};
-        size_t input_size = 0;
+        char output_file_name[256] = {0,};

[Noel Gordon, 2016/04/28 07:30:27]

char output_file_name[1024];

[radu.velea, 2016/04/28 08:17:25]

Done.

+        long int time_stamp = (long int)time(NULL);
 
         printf("Detected parametric curve type = %d\n", profile->redTRC->count);
 
-        sprintf(file_name, "qcms-test-%ld-parametric-gamma-%s.csv", (long int)time(NULL), profile->description);
-        printf("Writing input and output gamma tables to %s\n", file_name);
+        sprintf(output_file_name, "qcms-test-%ld-parametric-gamma-output-%s.csv", time_stamp, profile->description);
+        printf("Writing output gamma tables to %s\n", output_file_name);
 
         printf("gamma = %.6f, a = %.6f, b = %.6f, c = %.6f, d = %.6f, e = %.6f, f = %.6f\n",
                 profile->redTRC->parameter[0], profile->redTRC->parameter[1], profile->redTRC->parameter[2],
                 profile->redTRC->parameter[3], profile->redTRC->parameter[4], profile->redTRC->parameter[5],
                 profile->redTRC->parameter[6]);
 
         // Write output to stdout and tables into a csv file.
-        gamma_file = fopen(file_name, "w");
+        gamma_file = fopen(output_file_name, "w");
         fprintf(gamma_file, "Parametric gamma values for %s\n", profile->description);
         fprintf(gamma_file, "gamma, a, b, c, d, e, f\n");
         fprintf(gamma_file, "%.6f, %.6f, %.6f, %.6f, %.6f, %.6f, %.6f\n",
                 profile->redTRC->parameter[0], profile->redTRC->parameter[1], profile->redTRC->parameter[2],
                 profile->redTRC->parameter[3], profile->redTRC->parameter[4], profile->redTRC->parameter[5],
                 profile->redTRC->parameter[6]);
 
         get_input_gamma_table(in_path, &gamma_table_in, &input_size);
-        assert(input_size == gamma_table_size);
         if (!gamma_table_in) {
             fprintf(stderr, "Unable to compute input trc. Aborting\n");
             fclose(gamma_file);
             qcms_profile_release(profile);
             free(gamma_table_out);
             return EXIT_FAILURE;
         }
 
+        scale_factor = (float)(output_size - 1) / (input_size - 1);
+
+        fprintf(gamma_file, "\nInput curve size: %zu\nOutput curve size: %zu\n", input_size, output_size);
         fprintf(gamma_file, "\n\nInput gamma, Output gamma, LCMS Output gamma, Output gamma error\n");
 
-        p_table_out = gamma_table_out;
-        p_table_in = gamma_table_in;
+        for (i = 0; i < input_size; ++i) {
+            float input = gamma_table_in[i * 4] * inverse65535;
+            size_t out_index = (size_t)floor( i * scale_factor + 0.5);
+            float p = out_index / (output_size * 1.0);

[Noel Gordon, 2016/04/28 07:30:27]

What is the maximum value of |out_index| (assume curves are 256 input, 4096
output as an example). Call this maximum M.  What is the value of |p| when
out_index is M?

[radu.velea, 2016/04/28 08:17:25]

4095 / 4096 * 1.0, which comes short of 1.0 (which may explain why lcms final
value is not 1.0 in our tables).
we could change this to out_index / ((output_size - 1) * 1.0), since we adjusted
the scale to (float)(output_size - 1) / (input_size - 1);

+            float reference_out = clamp_float(evaluate_parametric_curve(type, profile->redTRC->parameter, p));

[Noel Gordon, 2016/04/28 07:30:27]

the "_out"'s are maybe not needed, perhaps use

eference_out -> reference

[radu.velea, 2016/04/28 08:17:25]

Done.

+            float actual_out = gamma_table_out[out_index * 4] * inverse65535;

[Noel Gordon, 2016/04/28 07:30:27]

actual_out -> actual

[radu.velea, 2016/04/28 08:17:25]

Done.

+            float error_out = fabs(actual_out - reference_out);

[Noel Gordon, 2016/04/28 07:30:27]

error_out -> difference

[radu.velea, 2016/04/28 08:17:25]

Done.

 
-        for (i = 0; i < gamma_table_size; ++i) {
-            float p = i / (gamma_table_size * 1.0);
-            float reference_out = clamp_float(evaluate_parametric_curve(type, profile->redTRC->parameter, p));
-            float actual_out = *p_table_out * inverse65535;
-            float error_out = fabs(actual_out - reference_out);
-            float input = *p_table_in * inverse65535;
-
-            fprintf(gamma_file, "%.6f, %.6f, %6f, %6f\n",input, actual_out, reference_out, error_out);
-
-            p_table_out += 4; // Skip other channels.
-            p_table_in += 4; // Skip other channels.
+            fprintf(gamma_file, "%.6f, %.6f, %6f, %6f\n", input, actual_out, reference_out, error_out);
         }
 
+        fprintf(gamma_file, "\nNote: the output curves we down sampled by a factor of %zu / %zu\n",
+                output_size, input_size);
+
+        fclose(gamma_file);
         free(gamma_table_in);
-        fclose(gamma_file);
     }
 
     qcms_profile_release(profile);
     free(gamma_table_out);
 
     return 0;
 }
 
 struct qcms_test_case qcms_test_output_trc_info = {
         "qcms_test_output_trc",
         qcms_test_output_trc,
         QCMS_TEST_DISABLED
 };