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 35 DEF_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