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Side by Side Diff: tools/visualize_color_gamut.cpp

Issue 1972343002: Simple program for visualizing gamuts (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Make output filename a flag Created 4 years, 7 months ago
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1 /*
2 * Copyright 2016 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "Resources.h"
9
10 #include "SkBitmap.h"
11 #include "SkCanvas.h"
12 #include "SkCodec.h"
13 #include "SkColorSpace.h"
14 #include "SkCommandLineFlags.h"
15 #include "SkForceLinking.h"
16 #include "SkImageEncoder.h"
17 #include "SkMatrix44.h"
18 #include "SkOSFile.h"
19
20 __SK_FORCE_IMAGE_DECODER_LINKING;
21
22 DEFINE_string2(input, i, "input.png", "A path to the input image.");
23 DEFINE_string2(output, o, "output.png", "A path to the output image.");
24
25 /**
26 * Loads the triangular gamut as a set of three points.
27 */
28 static void load_gamut(SkPoint rgb[], const SkMatrix44& xyz) {
29 // rx = rX / (rX + rY + rZ)
30 // ry = rX / (rX + rY + rZ)
31 // gx, gy, bx, and gy are calulcated similarly.
32 float rSum = xyz.get(0, 0) + xyz.get(0, 1) + xyz.get(0, 2);
33 float gSum = xyz.get(1, 0) + xyz.get(1, 1) + xyz.get(1, 2);
34 float bSum = xyz.get(2, 0) + xyz.get(2, 1) + xyz.get(2, 2);
35 rgb[0].fX = xyz.get(0, 0) / rSum;
36 rgb[0].fY = xyz.get(0, 1) / rSum;
37 rgb[1].fX = xyz.get(1, 0) / gSum;
38 rgb[1].fY = xyz.get(1, 1) / gSum;
39 rgb[2].fX = xyz.get(2, 0) / bSum;
40 rgb[2].fY = xyz.get(2, 1) / bSum;
41 }
42
43 /**
44 * Calculates the area of the triangular gamut.
45 */
46 float calculate_area(SkPoint abc[]) {
47 SkPoint a = abc[0];
48 SkPoint b = abc[1];
49 SkPoint c = abc[2];
50 return 0.5f * SkTAbs(a.fX*b.fY + b.fX*c.fY - a.fX*c.fY - c.fX*b.fY - b.fX*a. fY);
51 }
52
53 int main(int argc, char** argv) {
54 SkCommandLineFlags::SetUsage(
55 "Usage: visualize_color_gamut --input <path to input image>"
56 "--output <path to output image>\n"
57 "Description: Writes a visualization of the color gamut to the outpu t image\n");
58 SkCommandLineFlags::Parse(argc, argv);
59 const char* input = FLAGS_input[0];
60 const char* output = FLAGS_output[0];
61 if (!input || !output) {
62 SkCommandLineFlags::PrintUsage();
63 return -1;
64 }
65
66 SkAutoTUnref<SkData> data(SkData::NewFromFileName(input));
67 if (!data) {
68 SkDebugf("Cannot find input image.\n");
69 return -1;
70 }
71 SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(data));
72 if (!codec) {
73 SkDebugf("Invalid input image.\n");
74 return -1;
75 }
76
77 // Load a graph of the CIE XYZ color gamut.
78 SkBitmap bitmap;
79 if (!GetResourceAsBitmap("gamut.png", &bitmap)) {
80 SkDebugf("Program failure.\n");
81 return -1;
82 }
83 SkCanvas canvas(bitmap);
84
85 sk_sp<SkColorSpace> colorSpace = sk_ref_sp(codec->getColorSpace());
86 if (!colorSpace) {
87 SkDebugf("Image had no embedded color space information. Defaulting to sRGB.\n");
88 colorSpace = SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named);
89 }
90
91 // Calculate the points in the gamut from the XYZ values.
92 SkMatrix44 xyz = colorSpace->xyz();
93 SkPoint rgb[4];
94 load_gamut(rgb, xyz);
95
96 // Report the XYZ values.
97 SkDebugf(" X Y Z\n");
98 SkDebugf("Red %.2f %.2f %.2f\n", xyz.get(0, 0), xyz.get(0, 1), xyz.get(0, 2));
99 SkDebugf("Green %.2f %.2f %.2f\n", xyz.get(1, 0), xyz.get(1, 1), xyz.get(1, 2));
100 SkDebugf("Blue %.2f %.2f %.2f\n", xyz.get(2, 0), xyz.get(2, 1), xyz.get(2, 2));
101
102 // Report the area of the gamut.
103 SkDebugf("Area of Gamut: %g\n", calculate_area(rgb));
104
105 // Now transform the points so they can be drawn on our canvas. We use 1000 pixels
106 // to represent the space from 0 to 1. Note that the graph is at an offset of (50, 50).
107 // Also note that y increases as we move down the canvas.
108 rgb[0].fX = 50 + 1000*rgb[0].fX;
109 rgb[0].fY = 50 + 1000*(1 - rgb[0].fY);
110 rgb[1].fX = 50 + 1000*rgb[1].fX;
111 rgb[1].fY = 50 + 1000*(1 - rgb[1].fY);
112 rgb[2].fX = 50 + 1000*rgb[2].fX;
113 rgb[2].fY = 50 + 1000*(1 - rgb[2].fY);
114
115 // Repeat the first point to connect the polygon.
116 rgb[3] = rgb[0];
117
118 SkPaint paint;
119 canvas.drawPoints(SkCanvas::kPolygon_PointMode, 4, rgb, paint);
120
121 // Finally, encode the result to out.png.
122 SkAutoTUnref<SkData> out(SkImageEncoder::EncodeData(bitmap, SkImageEncoder:: kPNG_Type, 100));
123 if (!out) {
124 SkDebugf("Failed to encode output.\n");
125 return -1;
126 }
127 SkFILEWStream stream(output);
128 bool result = stream.write(out->data(), out->size());
129 if (!result) {
130 SkDebugf("Failed to write output.\n");
131 return -1;
132 }
133
134 return 0;
135 }
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