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Unified Diff: gm/labpcsdemo.cpp

Issue 2389983002: Refactored SkColorSpace and added in a Lab PCS GM (Closed)
Patch Set: migrated call from SkColorSpace_Base::makeLinearGamma() to SkColorSpace_XYZ::makeLinearGamma() Created 4 years, 2 months ago
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Index: gm/labpcsdemo.cpp
diff --git a/gm/labpcsdemo.cpp b/gm/labpcsdemo.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..4bd9ed8140f43790397637c48843fcacfb2126c1
--- /dev/null
+++ b/gm/labpcsdemo.cpp
@@ -0,0 +1,272 @@
+/*
+ * 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 <cmath>
+#include "gm.h"
+#include "Resources.h"
+#include "SkCodec.h"
+#include "SkColorSpace_Base.h"
+#include "SkColorSpace_A2B.h"
+#include "SkColorSpacePriv.h"
+#include "SkData.h"
+#include "SkFloatingPoint.h"
+#include "SkImageInfo.h"
+#include "SkScalar.h"
+#include "SkSRGB.h"
+#include "SkStream.h"
+#include "SkSurface.h"
+#include "SkTypes.h"
+
+static inline void interp_3d_clut(float dst[3], float src[3], const SkColorLookUpTable* colorLUT) {
+ // Call the src components x, y, and z.
+ uint8_t maxX = colorLUT->fGridPoints[0] - 1;
+ uint8_t maxY = colorLUT->fGridPoints[1] - 1;
+ uint8_t maxZ = colorLUT->fGridPoints[2] - 1;
+
+ // An approximate index into each of the three dimensions of the table.
+ float x = src[0] * maxX;
+ float y = src[1] * maxY;
+ float z = src[2] * maxZ;
+
+ // This gives us the low index for our interpolation.
+ int ix = sk_float_floor2int(x);
+ int iy = sk_float_floor2int(y);
+ int iz = sk_float_floor2int(z);
+
+ // Make sure the low index is not also the max index.
+ ix = (maxX == ix) ? ix - 1 : ix;
+ iy = (maxY == iy) ? iy - 1 : iy;
+ iz = (maxZ == iz) ? iz - 1 : iz;
+
+ // Weighting factors for the interpolation.
+ float diffX = x - ix;
+ float diffY = y - iy;
+ float diffZ = z - iz;
+
+ // Constants to help us navigate the 3D table.
+ // Ex: Assume x = a, y = b, z = c.
+ // table[a * n001 + b * n010 + c * n100] logically equals table[a][b][c].
+ const int n000 = 0;
+ const int n001 = 3 * colorLUT->fGridPoints[1] * colorLUT->fGridPoints[2];
+ const int n010 = 3 * colorLUT->fGridPoints[2];
+ const int n011 = n001 + n010;
+ const int n100 = 3;
+ const int n101 = n100 + n001;
+ const int n110 = n100 + n010;
+ const int n111 = n110 + n001;
+
+ // Base ptr into the table.
+ const float* ptr = &(colorLUT->table()[ix*n001 + iy*n010 + iz*n100]);
+
+ // The code below performs a tetrahedral interpolation for each of the three
+ // dst components. Once the tetrahedron containing the interpolation point is
+ // identified, the interpolation is a weighted sum of grid values at the
+ // vertices of the tetrahedron. The claim is that tetrahedral interpolation
+ // provides a more accurate color conversion.
+ // blogs.mathworks.com/steve/2006/11/24/tetrahedral-interpolation-for-colorspace-conversion/
+ //
+ // I have one test image, and visually I can't tell the difference between
+ // tetrahedral and trilinear interpolation. In terms of computation, the
+ // tetrahedral code requires more branches but less computation. The
+ // SampleICC library provides an option for the client to choose either
+ // tetrahedral or trilinear.
+ for (int i = 0; i < 3; i++) {
+ if (diffZ < diffY) {
+ if (diffZ < diffX) {
+ dst[i] = (ptr[n000] + diffZ * (ptr[n110] - ptr[n010]) +
+ diffY * (ptr[n010] - ptr[n000]) +
+ diffX * (ptr[n111] - ptr[n110]));
+ } else if (diffY < diffX) {
+ dst[i] = (ptr[n000] + diffZ * (ptr[n111] - ptr[n011]) +
+ diffY * (ptr[n011] - ptr[n001]) +
+ diffX * (ptr[n001] - ptr[n000]));
+ } else {
+ dst[i] = (ptr[n000] + diffZ * (ptr[n111] - ptr[n011]) +
+ diffY * (ptr[n010] - ptr[n000]) +
+ diffX * (ptr[n011] - ptr[n010]));
+ }
+ } else {
+ if (diffZ < diffX) {
+ dst[i] = (ptr[n000] + diffZ * (ptr[n101] - ptr[n001]) +
+ diffY * (ptr[n111] - ptr[n101]) +
+ diffX * (ptr[n001] - ptr[n000]));
+ } else if (diffY < diffX) {
+ dst[i] = (ptr[n000] + diffZ * (ptr[n100] - ptr[n000]) +
+ diffY * (ptr[n111] - ptr[n101]) +
+ diffX * (ptr[n101] - ptr[n100]));
+ } else {
+ dst[i] = (ptr[n000] + diffZ * (ptr[n100] - ptr[n000]) +
+ diffY * (ptr[n110] - ptr[n100]) +
+ diffX * (ptr[n111] - ptr[n110]));
+ }
+ }
+
+ // Increment the table ptr in order to handle the next component.
+ // Note that this is the how table is designed: all of nXXX
+ // variables are multiples of 3 because there are 3 output
+ // components.
+ ptr++;
+ }
+}
+
+
+/**
+ * This tests decoding from a Lab source image and displays on the left
+ * the image as raw RGB values, and on the right a Lab PCS.
+ * It currently does NOT apply a/b/m-curves, as in the .icc profile
+ * We are testing it on these are all identity transforms.
+ */
+class LabPCSDemoGM : public skiagm::GM {
+public:
+ LabPCSDemoGM()
+ : fWidth(1080)
+ , fHeight(480)
+ {}
+
+protected:
+
+
+ SkString onShortName() override {
+ return SkString("labpcsdemo");
+ }
+
+ SkISize onISize() override {
+ return SkISize::Make(fWidth, fHeight);
+ }
+
+ void onDraw(SkCanvas* canvas) override {
+ canvas->drawColor(SK_ColorGREEN);
+ const char* filename = "brickwork-texture.jpg";
+ renderImage(canvas, filename, 0, false);
+ renderImage(canvas, filename, 1, true);
+ }
+
+ void renderImage(SkCanvas* canvas, const char* filename, int col, bool convertLabToXYZ) {
+ SkBitmap bitmap;
+ SkStream* stream(GetResourceAsStream(filename));
+ if (stream == nullptr) {
+ return;
+ }
+ std::unique_ptr<SkCodec> codec(SkCodec::NewFromStream(stream));
+
+
+ // srgb_lab_pcs.icc is an elaborate way to specify sRGB but uses
+ // Lab as the PCS, so we can take any arbitrary image that should
+ // be sRGB and this should show a reasonable image
+ const SkString iccFilename(GetResourcePath("icc_profiles/srgb_lab_pcs.icc"));
+ sk_sp<SkData> iccData = SkData::MakeFromFileName(iccFilename.c_str());
+ if (iccData == nullptr) {
+ return;
+ }
+ sk_sp<SkColorSpace> colorSpace = SkColorSpace::NewICC(iccData->bytes(), iccData->size());
+
+ const int imageWidth = codec->getInfo().width();
+ const int imageHeight = codec->getInfo().height();
+ // Using nullptr as the color space instructs the codec to decode in legacy mode,
+ // meaning that we will get the raw encoded bytes without any color correction.
+ SkImageInfo imageInfo = SkImageInfo::Make(imageWidth, imageHeight, kN32_SkColorType,
+ kOpaque_SkAlphaType, nullptr);
+ bitmap.allocPixels(imageInfo);
+ codec->getPixels(imageInfo, bitmap.getPixels(), bitmap.rowBytes());
+ if (convertLabToXYZ) {
+ SkASSERT(SkColorSpace_Base::Type::kA2B == as_CSB(colorSpace)->type());
+ SkColorSpace_A2B& cs = *static_cast<SkColorSpace_A2B*>(colorSpace.get());
+ bool printConversions = false;
+ SkASSERT(cs.colorLUT());
+ // We're skipping evaluating the TRCs and the matrix here since they aren't
+ // in the ICC profile initially used here.
+ SkASSERT(kLinear_SkGammaNamed == cs.aCurveNamed());
+ SkASSERT(kLinear_SkGammaNamed == cs.mCurveNamed());
+ SkASSERT(kLinear_SkGammaNamed == cs.bCurveNamed());
+ SkASSERT(cs.matrix().isIdentity());
+ for (int y = 0; y < imageHeight; ++y) {
+ for (int x = 0; x < imageWidth; ++x) {
+ uint32_t& p = *bitmap.getAddr32(x, y);
+ const int r = SkColorGetR(p);
+ const int g = SkColorGetG(p);
+ const int b = SkColorGetB(p);
+ if (printConversions) {
+ SkColorSpacePrintf("\nraw = (%d, %d, %d)\t", r, g, b);
+ }
+
+ float lab[4] = { r * (1.f/255.f), g * (1.f/255.f), b * (1.f/255.f), 1.f };
+
+ interp_3d_clut(lab, lab, cs.colorLUT());
+
+ // Lab has ranges [0,100] for L and [-128,127] for a and b
+ // but the ICC profile loader stores as [0,1]. The ICC
+ // specifies an offset of -128 to convert.
+ // note: formula could be adjusted to remove this conversion,
+ // but for now let's keep it like this for clarity until
+ // an optimized version is added.
+ lab[0] *= 100.f;
+ lab[1] = 255.f * lab[1] - 128.f;
+ lab[2] = 255.f * lab[2] - 128.f;
+ if (printConversions) {
+ SkColorSpacePrintf("Lab = < %f, %f, %f >\n", lab[0], lab[1], lab[2]);
+ }
+
+ // convert from Lab to XYZ
+ float Y = (lab[0] + 16.f) * (1.f/116.f);
+ float X = lab[1] * (1.f/500.f) + Y;
+ float Z = Y - (lab[2] * (1.f/200.f));
+ float cubed;
+ cubed = X*X*X;
+ if (cubed > 0.008856f)
+ X = cubed;
+ else
+ X = (X - (16.f/116.f)) * (1.f/7.787f);
+ cubed = Y*Y*Y;
+ if (cubed > 0.008856f)
+ Y = cubed;
+ else
+ Y = (Y - (16.f/116.f)) * (1.f/7.787f);
+ cubed = Z*Z*Z;
+ if (cubed > 0.008856f)
+ Z = cubed;
+ else
+ Z = (Z - (16.f/116.f)) * (1.f/7.787f);
+
+ // adjust to D50 illuminant
+ X *= 0.96422f;
+ Y *= 1.00000f;
+ Z *= 0.82521f;
+
+ if (printConversions) {
+ SkColorSpacePrintf("XYZ = (%4f, %4f, %4f)\t", X, Y, Z);
+ }
+
+ // convert XYZ -> linear sRGB
+ Sk4f lRGB( 3.1338561f*X - 1.6168667f*Y - 0.4906146f*Z,
+ -0.9787684f*X + 1.9161415f*Y + 0.0334540f*Z,
+ 0.0719453f*X - 0.2289914f*Y + 1.4052427f*Z,
+ 1.f);
+ // and apply sRGB gamma
+ Sk4i sRGB = sk_linear_to_srgb(lRGB);
+ if (printConversions) {
+ SkColorSpacePrintf("sRGB = (%d, %d, %d)\n", sRGB[0], sRGB[1], sRGB[2]);
+ }
+ p = SkColorSetRGB(sRGB[0], sRGB[1], sRGB[2]);
+ }
+ }
+ }
+ const int freeWidth = fWidth - 2*imageWidth;
+ const int freeHeight = fHeight - imageHeight;
+ canvas->drawBitmap(bitmap,
+ static_cast<SkScalar>((col+1) * (freeWidth / 3) + col*imageWidth),
+ static_cast<SkScalar>(freeHeight / 2));
+ ++col;
+ }
+
+private:
+ const int fWidth;
+ const int fHeight;
+
+ typedef skiagm::GM INHERITED;
+};
+
+DEF_GM( return new LabPCSDemoGM; )
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