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/SkFilterQuality.h" 12 #include "include/core/SkImage.h" 13 #include "include/core/SkMatrix.h" 14 #include "include/core/SkPaint.h" 15 #include "include/core/SkRect.h" 16 #include "include/core/SkRefCnt.h" 17 #include "include/core/SkShader.h" 18 #include "include/core/SkSurface.h" 19 #include "include/core/SkTileMode.h" 20 21 // This GM reproduces skia:6783, which demonstrated a bug in repeat and mirror 22 // image sampling tiling modes as implemented in software. We want to tile to 23 // [0,limit), and the old incorrect logic was: 24 // 25 // limit = ulp_before(limit) 26 // val = val - floor(val/limit)*limit (This is repeat; mirror is similar.) 27 // 28 // while the correct logic is more like: 29 // 30 // val = val - floor(val/limit)*limit 31 // val = min(val, ulp_before(limit)) 32 // 33 // You would see ugly jaggies on the blue/yellow edge near the bottom left if 34 // the bug were still present. All stripes should now look roughly the same. 35 36 DEF_SIMPLE_GM(bug6783, canvas, 500, 500) { 37 sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(100, 100); 38 39 SkPaint p; 40 p.setColor(SK_ColorYELLOW); 41 surface->getCanvas()->drawPaint(p); 42 p.setColor(SK_ColorBLUE); 43 surface->getCanvas()->drawRect(SkRect::MakeWH(50, 100), p); 44 45 sk_sp<SkImage> img = surface->makeImageSnapshot(); 46 47 SkMatrix m = SkMatrix::Concat(SkMatrix::MakeTrans(25, 214), 48 SkMatrix::MakeScale(2, 2)); 49 m.preSkew(0.5f, 0.5f); 50 51 // The bug was present at all filter levels, but you might not notice it at kNone. 52 p.setFilterQuality(kLow_SkFilterQuality); 53 54 // It's only important to repeat or mirror in x to show off the bug. 55 p.setShader(img->makeShader(SkTileMode::kRepeat, SkTileMode::kClamp, &m)); 56 canvas->drawPaint(p); 57 } 58