blob: ead77b3db817a958826a79cad764de2a08178a67 [file] [log] [blame]
* Copyright 2017 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include "gm/gm.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkColor.h"
#include "include/core/SkImage.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkPaint.h"
#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkShader.h"
#include "include/core/SkSurface.h"
#include "include/core/SkTileMode.h"
// This GM reproduces skia:6783, which demonstrated a bug in repeat and mirror
// image sampling tiling modes as implemented in software. We want to tile to
// [0,limit), and the old incorrect logic was:
// limit = ulp_before(limit)
// val = val - floor(val/limit)*limit (This is repeat; mirror is similar.)
// while the correct logic is more like:
// val = val - floor(val/limit)*limit
// val = min(val, ulp_before(limit))
// You would see ugly jaggies on the blue/yellow edge near the bottom left if
// the bug were still present. All stripes should now look roughly the same.
DEF_SIMPLE_GM(bug6783, canvas, 500, 500) {
sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(100, 100);
SkPaint p;
surface->getCanvas()->drawRect(SkRect::MakeWH(50, 100), p);
sk_sp<SkImage> img = surface->makeImageSnapshot();
SkMatrix m = SkMatrix::Translate(25, 214) * SkMatrix::Scale(2, 2);
m.preSkew(0.5f, 0.5f);
// The bug was present at all filter levels, but you might not notice it at nearest.
SkSamplingOptions sampling(SkFilterMode::kLinear);
// It's only important to repeat or mirror in x to show off the bug.
p.setShader(img->makeShader(SkTileMode::kRepeat, SkTileMode::kClamp, sampling, m));