gm/gamma.cpp

   1 /*
   2  * Copyright 2015 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 "gm.h"
   9 #include "sk_tool_utils.h"
  10
  11 #include "Resources.h"
  12 #include "SkBlendModePriv.h"
  13 #include "SkGradientShader.h"
  14 #include "SkPM4fPriv.h"
  15
  16 DEF_SIMPLE_GM(gamma, canvas, 850, 200) {
  17     SkPaint p;
  18     const SkScalar sz = 50.0f;
  19     const int szInt = SkScalarTruncToInt(sz);
  20     const SkScalar tx = sz + 15.0f;
  21     const SkRect r = SkRect::MakeXYWH(0, 0, sz, sz);
  22     SkShader::TileMode rpt = SkShader::kRepeat_TileMode;
  23     auto srgbColorSpace = SkColorSpace::MakeSRGB();
  24
  25     SkBitmap ditherBmp;
  26     ditherBmp.allocN32Pixels(2, 2);
  27     SkPMColor* pixels = reinterpret_cast<SkPMColor*>(ditherBmp.getPixels());
  28     pixels[0] = pixels[3] = SkPackARGB32(0xFF, 0xFF, 0xFF, 0xFF);
  29     pixels[1] = pixels[2] = SkPackARGB32(0xFF, 0, 0, 0);
  30
  31     SkBitmap linearGreyBmp;
  32     SkImageInfo linearGreyInfo = SkImageInfo::MakeN32(szInt, szInt, kOpaque_SkAlphaType, nullptr);
  33     linearGreyBmp.allocPixels(linearGreyInfo);
  34     linearGreyBmp.eraseARGB(0xFF, 0x7F, 0x7F, 0x7F);
  35
  36     SkBitmap srgbGreyBmp;
  37     SkImageInfo srgbGreyInfo = SkImageInfo::MakeN32(szInt, szInt, kOpaque_SkAlphaType,
  38                                                     srgbColorSpace);
  39     srgbGreyBmp.allocPixels(srgbGreyInfo);
  40     // 0xBC = 255 * linear_to_srgb(0.5f)
  41     srgbGreyBmp.eraseARGB(0xFF, 0xBC, 0xBC, 0xBC);
  42
  43     SkBitmap mipmapBmp;
  44     SkImageInfo mipmapInfo = SkImageInfo::Make(2, 2, kN32_SkColorType, kOpaque_SkAlphaType,
  45                                                srgbColorSpace);
  46     mipmapBmp.allocPixels(mipmapInfo);
  47     SkPMColor* mipmapPixels = reinterpret_cast<SkPMColor*>(mipmapBmp.getPixels());
  48     unsigned s25 = 0x89;    // 255 * linear_to_srgb(0.25f)
  49     unsigned s75 = 0xE1;    // 255 * linear_to_srgb(0.75f)
  50     mipmapPixels[0] = mipmapPixels[3] = SkPackARGB32(0xFF, s25, s25, s25);
  51     mipmapPixels[1] = mipmapPixels[2] = SkPackARGB32(0xFF, s75, s75, s75);
  52
  53     SkPaint textPaint;
  54     textPaint.setAntiAlias(true);
  55     textPaint.setColor(SK_ColorWHITE);
  56     sk_tool_utils::set_portable_typeface(&textPaint);
  57
  58     // Helpers:
  59     auto advance = [&]() {
  60         canvas->translate(tx, 0);
  61         p.reset();
  62     };
  63
  64     auto nextRect = [&](const char* label, const char* label2) {
  65         canvas->drawRect(r, p);
  66         canvas->drawString(label, 0, sz + textPaint.getFontSpacing(), textPaint);
  67         if (label2) {
  68             canvas->drawString(label2, 0, sz + 2 * textPaint.getFontSpacing(),
  69                              textPaint);
  70         }
  71         advance();
  72     };
  73
  74     auto nextBitmap = [&](const SkBitmap& bmp, const char* label) {
  75         canvas->drawBitmap(bmp, 0, 0);
  76         canvas->drawString(label, 0, sz + textPaint.getFontSpacing(), textPaint);
  77         advance();
  78     };
  79
  80     auto nextXferRect = [&](SkColor srcColor, SkBlendMode mode, SkColor dstColor) {
  81         p.setColor(dstColor);
  82         canvas->drawRect(r, p);
  83         p.setColor(srcColor);
  84         p.setBlendMode(mode);
  85         canvas->drawRect(r, p);
  86
  87         SkString srcText = SkStringPrintf("%08X", srcColor);
  88         SkString dstText = SkStringPrintf("%08X", dstColor);
  89         canvas->drawString(srcText, 0, sz + textPaint.getFontSpacing(),
  90                          textPaint);
  91         const char* modeName = SkBlendMode_Name(mode);
  92         canvas->drawString(modeName, 0, sz + 2 * textPaint.getFontSpacing(),
  93                          textPaint);
  94         canvas->drawString(dstText, 0, sz + 3 * textPaint.getFontSpacing(),
  95                          textPaint);
  96         advance();
  97     };
  98
  99     // Necessary for certain Xfermode tests to work (ie some of them output white @ 50% alpha):
 100     canvas->clear(SK_ColorBLACK);
 101
 102     // *Everything* should be perceptually 50% grey. Only the first rectangle
 103     // is guaranteed to draw that way, though.
 104     canvas->save();
 105
 106     // Black/white dither, pixel perfect. This is ground truth.
 107     p.setShader(SkShader::MakeBitmapShader(ditherBmp, rpt, rpt));
 108     p.setFilterQuality(SkFilterQuality::kNone_SkFilterQuality);
 109     nextRect("Dither", "Reference");
 110
 111     // Black/white dither, sampled at half-texel offset. Tests bilerp.
 112     // NOTE: We need to apply a non-identity scale and/or rotation to trick
 113     // the raster pipeline into *not* snapping to nearest.
 114     SkMatrix offsetMatrix = SkMatrix::Concat(
 115         SkMatrix::MakeScale(-1.0f), SkMatrix::MakeTrans(0.5f, 0.0f));
 116     p.setShader(SkShader::MakeBitmapShader(ditherBmp, rpt, rpt, &offsetMatrix));
 117     p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
 118     nextRect("Dither", "Bilerp");
 119
 120     // Black/white dither, scaled down by 2x. Tests minification.
 121     SkMatrix scaleMatrix = SkMatrix::MakeScale(0.5f);
 122     p.setShader(SkShader::MakeBitmapShader(ditherBmp, rpt, rpt, &scaleMatrix));
 123     p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
 124     nextRect("Dither", "Scale");
 125
 126     // 25%/75% dither, scaled down by 2x. Tests ALL aspects of minification. Specifically, are
 127     // sRGB sources decoded to linear before computing mipmaps?
 128     p.setShader(SkShader::MakeBitmapShader(mipmapBmp, rpt, rpt, &scaleMatrix));
 129     p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
 130     nextRect("MipMaps", 0);
 131
 132     // 50% grey via paint color. Paint color (SkColor) is specified to be sRGB!
 133     p.setColor(0xffbcbcbc);
 134     nextRect("Color", 0);
 135
 136     {
 137         // Black -> White gradient, scaled to sample just the middle.
 138         // Tests gradient interpolation.
 139         SkPoint points[2] = {
 140             SkPoint::Make(0 - (sz * 10), 0),
 141             SkPoint::Make(sz + (sz * 10), 0)
 142         };
 143         SkColor colors[2] = { SK_ColorBLACK, SK_ColorWHITE };
 144         p.setShader(SkGradientShader::MakeLinear(points, colors, nullptr, 2,
 145                                                  SkShader::kClamp_TileMode));
 146         nextRect("Gradient", "Interpolation");
 147     }
 148
 149     {
 150         // Shallow gradient around 50% (perceptual) gray. Endpoints are SkColor, so sRGB.
 151         // Tests gamma-correction of gradient stops before interpolation in two-stop case
 152         SkPoint points[2] = {
 153             SkPoint::Make(0, 0),
 154             SkPoint::Make(sz, 0)
 155         };
 156         SkColor colors[2] = { 0xffbbbbbb, 0xffbdbdbd };
 157         p.setShader(SkGradientShader::MakeLinear(points, colors, nullptr, 2,
 158                                                  SkShader::kClamp_TileMode));
 159         nextRect("Gradient", "Endpoints");
 160     }
 161
 162     {
 163         // Shallow 3-stop gradient around 50% (perceptual) gray. Endpoints are SkColor, so sRGB.
 164         // Tests gamma-correction of gradient stops before interpolation in three-stop case
 165         SkPoint points[2] = {
 166             SkPoint::Make(0, 0),
 167             SkPoint::Make(sz, 0)
 168         };
 169         SkColor colors[3] = { 0xffbbbbbb, 0xffbdbdbd, 0xffbbbbbb };
 170         p.setShader(SkGradientShader::MakeLinear(points, colors, nullptr, 3,
 171                                                  SkShader::kClamp_TileMode));
 172         nextRect("Gradient", "3-Stop");
 173     }
 174
 175     {
 176         // Shallow N-stop gradient around 50% (perceptual) gray. Endpoints are SkColor, so sRGB.
 177         // Tests gamma-correction of gradient stops before interpolation in texture implementation
 178         SkPoint points[2] = {
 179             SkPoint::Make(0, 0),
 180             SkPoint::Make(sz, 0)
 181         };
 182         SkColor colors[5] = { 0xffbbbbbb, 0xffbdbdbd, 0xffbbbbbb, 0xffbdbdbd, 0xffbbbbbb };
 183         p.setShader(SkGradientShader::MakeLinear(points, colors, nullptr, 5,
 184                                                  SkShader::kClamp_TileMode));
 185         nextRect("Gradient", "Texture");
 186     }
 187
 188     // 50% grey from linear bitmap, with drawBitmap
 189     nextBitmap(linearGreyBmp, "Lnr BMP");
 190
 191     // 50% grey from sRGB bitmap, with drawBitmap
 192     nextBitmap(srgbGreyBmp, "sRGB BMP");
 193
 194     // Bitmap wrapped in a shader (linear):
 195     p.setShader(SkShader::MakeBitmapShader(linearGreyBmp, rpt, rpt));
 196     p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
 197     nextRect("Lnr BMP", "Shader");
 198
 199     // Bitmap wrapped in a shader (sRGB):
 200     p.setShader(SkShader::MakeBitmapShader(srgbGreyBmp, rpt, rpt));
 201     p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
 202     nextRect("sRGB BMP", "Shader");
 203
 204     // Carriage return.
 205     canvas->restore();
 206     canvas->translate(0, 2 * sz);
 207
 208     // Xfermode tests, all done off-screen so certain modes work...
 209
 210     canvas->saveLayer(nullptr, nullptr);
 211
 212     nextXferRect(0x7fffffff, SkBlendMode::kSrcOver, SK_ColorBLACK);
 213     nextXferRect(0x7f000000, SkBlendMode::kSrcOver, SK_ColorWHITE);
 214
 215     nextXferRect(SK_ColorBLACK, SkBlendMode::kDstOver, 0x7fffffff);
 216     nextXferRect(SK_ColorWHITE, SkBlendMode::kSrcIn, 0x7fff00ff);
 217     nextXferRect(0x7fff00ff, SkBlendMode::kDstIn, SK_ColorWHITE);
 218
 219     // 0x89 = 255 * linear_to_srgb(0.25)
 220     nextXferRect(0xff898989, SkBlendMode::kPlus, 0xff898989);
 221
 222     // 0xDB = 255 * linear_to_srgb(sqrt(0.5))
 223     nextXferRect(0xffdbdbdb, SkBlendMode::kModulate, 0xffdbdbdb);
 224
 225     canvas->restore();
 226 }