Manually generated sRGB mipmaps.

gm/gamma.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 
 #include "Resources.h"
 #include "SkGradientShader.h"
 
-DEF_SIMPLE_GM(gamma, canvas, 500, 200) {
+DEF_SIMPLE_GM(gamma, canvas, 560, 200) {
     SkPaint p;
     const SkScalar sz = 50.0f;
     const int szInt = SkScalarTruncToInt(sz);
     const SkScalar tx = sz + 5.0f;
     const SkRect r = SkRect::MakeXYWH(0, 0, sz, sz);
     SkShader::TileMode rpt = SkShader::kRepeat_TileMode;
 
     SkBitmap ditherBmp;
     ditherBmp.allocN32Pixels(2, 2);
     SkPMColor* pixels = reinterpret_cast<SkPMColor*>(ditherBmp.getPixels());
     pixels[0] = pixels[3] = SkPackARGB32(0xFF, 0xFF, 0xFF, 0xFF);
     pixels[1] = pixels[2] = SkPackARGB32(0xFF, 0, 0, 0);
 
     SkBitmap linearGreyBmp;
     SkImageInfo linearGreyInfo = SkImageInfo::MakeN32(szInt, szInt, kOpaque_SkAlphaType,
                                                       kLinear_SkColorProfileType);
     linearGreyBmp.allocPixels(linearGreyInfo);
     linearGreyBmp.eraseARGB(0xFF, 0x7F, 0x7F, 0x7F);
 
     SkBitmap srgbGreyBmp;
     SkImageInfo srgbGreyInfo = SkImageInfo::MakeN32(szInt, szInt, kOpaque_SkAlphaType,
                                                     kSRGB_SkColorProfileType);
     srgbGreyBmp.allocPixels(srgbGreyInfo);
+    // 0xBC = 255 * linear_to_srgb(0.5f)
     srgbGreyBmp.eraseARGB(0xFF, 0xBC, 0xBC, 0xBC);
 
+    SkBitmap mipmapBmp;
+    SkImageInfo mipmapInfo = SkImageInfo::MakeN32(2, 2, kOpaque_SkAlphaType,
+                                                  kSRGB_SkColorProfileType);
+    mipmapBmp.allocPixels(mipmapInfo);
+    SkPMColor* mipmapPixels = reinterpret_cast<SkPMColor*>(mipmapBmp.getPixels());
+    // 0x89 = 255 * linear_to_srgb(0.25f)
+    mipmapPixels[0] = mipmapPixels[3] = SkPackARGB32(0xFF, 0x89, 0x89, 0x89);
+    // 0xE1 = 255 * linear_to_srgb(0.75f)
+    mipmapPixels[1] = mipmapPixels[2] = SkPackARGB32(0xFF, 0xE1, 0xE1, 0xE1);
+
     SkPaint textPaint;
     textPaint.setColor(SK_ColorWHITE);
 
     // Helpers:
     auto advance = [&]() {
         canvas->translate(tx, 0);
         p.reset();
     };
 
     auto nextRect = [&](const char* label, const char* label2) {
@@ skipping 51 matching lines @@
     p.setShader(SkShader::MakeBitmapShader(ditherBmp, rpt, rpt, &offsetMatrix));
     p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
     nextRect("Dither", "Bilerp");
 
     // Black/white dither, scaled down by 2x. Tests minification.
     SkMatrix scaleMatrix = SkMatrix::MakeScale(0.5f);
     p.setShader(SkShader::MakeBitmapShader(ditherBmp, rpt, rpt, &scaleMatrix));
     p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
     nextRect("Dither", "Scale");
 
+    // 25%/75% dither, scaled down by 2x. Tests ALL aspects of minification. Specifically, are
+    // sRGB sources decoded to linear before computing mipmaps?
+    p.setShader(SkShader::MakeBitmapShader(mipmapBmp, rpt, rpt, &scaleMatrix));
+    p.setFilterQuality(SkFilterQuality::kMedium_SkFilterQuality);
+    nextRect("MipMaps", 0);
+
     // 50% grey via paint color.
     p.setColor(0xff7f7f7f);
     nextRect("Color", 0);
 
     // Black -> White gradient, scaled to sample just the middle.
     // Tests gradient interpolation.
     SkPoint points[2] = {
         SkPoint::Make(0 - (sz * 10), 0),
         SkPoint::Make(sz + (sz * 10), 0)
     };
@@ skipping 37 matching lines @@
     nextXferRect(SK_ColorWHITE, SkXfermode::kSrcIn_Mode, 0x7fff00ff);
     nextXferRect(0x7fff00ff, SkXfermode::kDstIn_Mode, SK_ColorWHITE);
     nextXferRect(sqrtHalfWhite, SkXfermode::kSrcIn_Mode, sqrtHalfAlpha);
     nextXferRect(sqrtHalfAlpha, SkXfermode::kDstIn_Mode, sqrtHalfWhite);
 
     nextXferRect(0xff3f3f3f, SkXfermode::kPlus_Mode, 0xff3f3f3f);
     nextXferRect(sqrtHalfWhite, SkXfermode::kModulate_Mode, sqrtHalfWhite);
 
     canvas->restore();
 }