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skia2/gm/labpcsdemo.cpp
raftias 9488833428 Refactored SkColorSpace and added in a Lab PCS GM 
The refactoring breaks off A2B0 tag support into a separate
subclass of SkColorSpace_Base, while keeping the current
(besides CLUT) functionality in a XYZTRC subclass.

ICC profile loading is now aware of this and creates the A2B0
subclass when SkColorSpace::NewICC() is called on a profile
in need of the A2B0 functionality.

The LabPCSDemo GM loads a .icc profile containing a LAB PCS and
then runs a Lab->XYZ conversion on an image using it so we can
display it and test out the A2B0 SkColorSpace functionality,
sans a/b/m-curves, as well as the Lab->XYZ conversion code.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2389983002

Review-Url: https://codereview.chromium.org/2389983002
2016-10-18 10:02:52 -07:00

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/*
* 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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