gm/crbug_1156804.cpp

/*
 * Copyright 2020 Google LLC
 *
 * 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/SkPaint.h"
#include "include/core/SkRect.h"
#include "include/effects/SkImageFilters.h"

static void drawOne(SkCanvas* canvas, SkRect rect, float saveBorder, float sigma, SkColor c) {
    SkPaint sp;
    sp.setImageFilter(SkImageFilters::Blur(sigma, sigma, SkTileMode::kClamp, nullptr));
    SkPaint p;
    p.setColor(c);
    p.setAntiAlias(true);

    canvas->saveLayer(rect.makeOutset(saveBorder, saveBorder), &sp);
    canvas->drawRect(rect, p);
    canvas->restore();
}

DEF_SIMPLE_GM(crbug_1156804, canvas, 250, 250) {
    drawOne(canvas, SkRect::MakeXYWH( 64,  64, 25, 25),  1,  3, SK_ColorGREEN);
    drawOne(canvas, SkRect::MakeXYWH(164,  64, 25, 25), 30,  3, SK_ColorGREEN);
    // This one would draw incorrectly because the large sigma causes downscaling of the source
    // and the one-pixel border would make the downscaled image not contain trans-black at the
    // edges. Combined with the clamp mode on the blur filter it would "harden" the edge.
    drawOne(canvas, SkRect::MakeXYWH( 64, 164, 25, 25),  1, 20, SK_ColorRED);
    drawOne(canvas, SkRect::MakeXYWH(164, 164, 25, 25), 30, 20, SK_ColorGREEN);
}