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