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Unified 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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Index: tools/visualize_color_gamut.cpp
diff --git a/tools/visualize_color_gamut.cpp b/tools/visualize_color_gamut.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..8fdd9621853402278b0a349768250899c7c29b91
--- /dev/null
+++ b/tools/visualize_color_gamut.cpp
@@ -0,0 +1,135 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Resources.h"
+
+#include "SkBitmap.h"
+#include "SkCanvas.h"
+#include "SkCodec.h"
+#include "SkColorSpace.h"
+#include "SkCommandLineFlags.h"
+#include "SkForceLinking.h"
+#include "SkImageEncoder.h"
+#include "SkMatrix44.h"
+#include "SkOSFile.h"
+
+__SK_FORCE_IMAGE_DECODER_LINKING;
+
+DEFINE_string2(input, i, "input.png", "A path to the input image.");
+DEFINE_string2(output, o, "output.png", "A path to the output image.");
+
+/**
+ * Loads the triangular gamut as a set of three points.
+ */
+static void load_gamut(SkPoint rgb[], const SkMatrix44& xyz) {
+ // rx = rX / (rX + rY + rZ)
+ // ry = rX / (rX + rY + rZ)
+ // gx, gy, bx, and gy are calulcated similarly.
+ float rSum = xyz.get(0, 0) + xyz.get(0, 1) + xyz.get(0, 2);
+ float gSum = xyz.get(1, 0) + xyz.get(1, 1) + xyz.get(1, 2);
+ float bSum = xyz.get(2, 0) + xyz.get(2, 1) + xyz.get(2, 2);
+ rgb[0].fX = xyz.get(0, 0) / rSum;
+ rgb[0].fY = xyz.get(0, 1) / rSum;
+ rgb[1].fX = xyz.get(1, 0) / gSum;
+ rgb[1].fY = xyz.get(1, 1) / gSum;
+ rgb[2].fX = xyz.get(2, 0) / bSum;
+ rgb[2].fY = xyz.get(2, 1) / bSum;
+}
+
+/**
+ * Calculates the area of the triangular gamut.
+ */
+float calculate_area(SkPoint abc[]) {
+ SkPoint a = abc[0];
+ SkPoint b = abc[1];
+ SkPoint c = abc[2];
+ return 0.5f * SkTAbs(a.fX*b.fY + b.fX*c.fY - a.fX*c.fY - c.fX*b.fY - b.fX*a.fY);
+}
+
+int main(int argc, char** argv) {
+ SkCommandLineFlags::SetUsage(
+ "Usage: visualize_color_gamut --input <path to input image>"
+ "--output <path to output image>\n"
+ "Description: Writes a visualization of the color gamut to the output image\n");
+ SkCommandLineFlags::Parse(argc, argv);
+ const char* input = FLAGS_input[0];
+ const char* output = FLAGS_output[0];
+ if (!input || !output) {
+ SkCommandLineFlags::PrintUsage();
+ return -1;
+ }
+
+ SkAutoTUnref<SkData> data(SkData::NewFromFileName(input));
+ if (!data) {
+ SkDebugf("Cannot find input image.\n");
+ return -1;
+ }
+ SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(data));
+ if (!codec) {
+ SkDebugf("Invalid input image.\n");
+ return -1;
+ }
+
+ // Load a graph of the CIE XYZ color gamut.
+ SkBitmap bitmap;
+ if (!GetResourceAsBitmap("gamut.png", &bitmap)) {
+ SkDebugf("Program failure.\n");
+ return -1;
+ }
+ SkCanvas canvas(bitmap);
+
+ sk_sp<SkColorSpace> colorSpace = sk_ref_sp(codec->getColorSpace());
+ if (!colorSpace) {
+ SkDebugf("Image had no embedded color space information. Defaulting to sRGB.\n");
+ colorSpace = SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named);
+ }
+
+ // Calculate the points in the gamut from the XYZ values.
+ SkMatrix44 xyz = colorSpace->xyz();
+ SkPoint rgb[4];
+ load_gamut(rgb, xyz);
+
+ // Report the XYZ values.
+ SkDebugf(" X Y Z\n");
+ SkDebugf("Red %.2f %.2f %.2f\n", xyz.get(0, 0), xyz.get(0, 1), xyz.get(0, 2));
+ SkDebugf("Green %.2f %.2f %.2f\n", xyz.get(1, 0), xyz.get(1, 1), xyz.get(1, 2));
+ SkDebugf("Blue %.2f %.2f %.2f\n", xyz.get(2, 0), xyz.get(2, 1), xyz.get(2, 2));
+
+ // Report the area of the gamut.
+ SkDebugf("Area of Gamut: %g\n", calculate_area(rgb));
+
+ // Now transform the points so they can be drawn on our canvas. We use 1000 pixels
+ // to represent the space from 0 to 1. Note that the graph is at an offset of (50, 50).
+ // Also note that y increases as we move down the canvas.
+ rgb[0].fX = 50 + 1000*rgb[0].fX;
+ rgb[0].fY = 50 + 1000*(1 - rgb[0].fY);
+ rgb[1].fX = 50 + 1000*rgb[1].fX;
+ rgb[1].fY = 50 + 1000*(1 - rgb[1].fY);
+ rgb[2].fX = 50 + 1000*rgb[2].fX;
+ rgb[2].fY = 50 + 1000*(1 - rgb[2].fY);
+
+ // Repeat the first point to connect the polygon.
+ rgb[3] = rgb[0];
+
+ SkPaint paint;
+ canvas.drawPoints(SkCanvas::kPolygon_PointMode, 4, rgb, paint);
+
+ // Finally, encode the result to out.png.
+ SkAutoTUnref<SkData> out(SkImageEncoder::EncodeData(bitmap, SkImageEncoder::kPNG_Type, 100));
+ if (!out) {
+ SkDebugf("Failed to encode output.\n");
+ return -1;
+ }
+ SkFILEWStream stream(output);
+ bool result = stream.write(out->data(), out->size());
+ if (!result) {
+ SkDebugf("Failed to write output.\n");
+ return -1;
+ }
+
+ return 0;
+}
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