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