1/* 2* Copyright 2017 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/gm.h" 9#include "include/core/SkCanvas.h" 10#include "include/core/SkColor.h" 11#include "include/core/SkImage.h" 12#include "include/core/SkMatrix.h" 13#include "include/core/SkPaint.h" 14#include "include/core/SkRect.h" 15#include "include/core/SkRefCnt.h" 16#include "include/core/SkShader.h" 17#include "include/core/SkSurface.h" 18#include "include/core/SkTileMode.h" 19 20// This GM reproduces skia:6783, which demonstrated a bug in repeat and mirror 21// image sampling tiling modes as implemented in software. We want to tile to 22// [0,limit), and the old incorrect logic was: 23// 24// limit = ulp_before(limit) 25// val = val - floor(val/limit)*limit (This is repeat; mirror is similar.) 26// 27// while the correct logic is more like: 28// 29// val = val - floor(val/limit)*limit 30// val = min(val, ulp_before(limit)) 31// 32// You would see ugly jaggies on the blue/yellow edge near the bottom left if 33// the bug were still present. All stripes should now look roughly the same. 34 35DEF_SIMPLE_GM(bug6783, canvas, 500, 500) { 36 sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(100, 100); 37 38 SkPaint p; 39 p.setColor(SK_ColorYELLOW); 40 surface->getCanvas()->drawPaint(p); 41 p.setColor(SK_ColorBLUE); 42 surface->getCanvas()->drawRect(SkRect::MakeWH(50, 100), p); 43 44 sk_sp<SkImage> img = surface->makeImageSnapshot(); 45 46 SkMatrix m = SkMatrix::Translate(25, 214) * SkMatrix::Scale(2, 2); 47 m.preSkew(0.5f, 0.5f); 48 49 // The bug was present at all filter levels, but you might not notice it at nearest. 50 SkSamplingOptions sampling(SkFilterMode::kLinear); 51 52 // It's only important to repeat or mirror in x to show off the bug. 53 p.setShader(img->makeShader(SkTileMode::kRepeat, SkTileMode::kClamp, sampling, m)); 54 canvas->drawPaint(p); 55} 56