skia2/gm/bug6783.cpp
Mike Klein 0cc60b8bbd fix repeat/mirror sampling bleed
I think this has been broken since we tried to simplify this in
  https://skia-review.googlesource.com/16547

The HSW backend does still look a little wrong, but improved,
and the others seem fixed.  Can you see how this affects your
test cases, layout tests, etc?

BUG=skia:6783

Change-Id: I17957ac8100331bea5b64d674bf43105048b72f6
Reviewed-on: https://skia-review.googlesource.com/20548
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
2017-06-22 19:46:51 +00:00

48 lines
1.6 KiB
C++

/*
* 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.h"
#include "SkSurface.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;
p.setColor(SK_ColorYELLOW);
surface->getCanvas()->drawPaint(p);
p.setColor(SK_ColorBLUE);
surface->getCanvas()->drawRect(SkRect::MakeWH(50, 100), p);
sk_sp<SkImage> img = surface->makeImageSnapshot();
SkMatrix m = SkMatrix::Concat(SkMatrix::MakeTrans(25, 214),
SkMatrix::MakeScale(2, 2));
m.preSkew(0.5f, 0.5f);
// The bug was present at all filter levels, but you might not notice it at kNone.
p.setFilterQuality(kLow_SkFilterQuality);
// It's only important to repeat or mirror in x to show off the bug.
p.setShader(img->makeShader(SkShader::kRepeat_TileMode, SkShader::kClamp_TileMode, &m));
canvas->drawPaint(p);
}