gm/imagefilters.cpp

/*
 * Copyright 2015 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 "SkImageFilter.h"
#include "SkColorMatrixFilter.h"

/**
 *  Test drawing a primitive w/ an imagefilter (in this case, just matrix w/ identity) to see
 *  that we apply the xfermode *after* the image has been created and filtered, and not during
 *  the creation step (i.e. before it is filtered).
 *
 *  see https://bug.skia.org/3741
 */
static void do_draw(SkCanvas* canvas, SkXfermode::Mode mode, SkImageFilter* imf) {
        SkAutoCanvasRestore acr(canvas, true);
        canvas->clipRect(SkRect::MakeWH(220, 220));
        
        // want to force a layer, so modes like DstIn can combine meaningfully, but the final
        // image can still be shown against our default (opaque) background. non-opaque GMs
        // are a lot more trouble to compare/triage.
        canvas->saveLayer(nullptr, nullptr);
        canvas->drawColor(SK_ColorGREEN);

        SkPaint paint;
        paint.setAntiAlias(true);
        
        SkRect r0 = SkRect::MakeXYWH(10, 60, 200, 100);
        SkRect r1 = SkRect::MakeXYWH(60, 10, 100, 200);
        
        paint.setColor(SK_ColorRED);
        canvas->drawOval(r0, paint);

        paint.setColor(0x660000FF);
        paint.setImageFilter(imf);
        paint.setXfermodeMode(mode);
        canvas->drawOval(r1, paint);
}

DEF_SIMPLE_GM(imagefilters_xfermodes, canvas, 480, 480) {
        canvas->translate(10, 10);

        // just need an imagefilter to trigger the code-path (which creates a tmp layer)
        SkAutoTUnref<SkImageFilter> imf(SkImageFilter::CreateMatrixFilter(SkMatrix::I(),
                                                                          kNone_SkFilterQuality));

        const SkXfermode::Mode modes[] = {
            SkXfermode::kSrcATop_Mode, SkXfermode::kDstIn_Mode
        };
        
        for (size_t i = 0; i < SK_ARRAY_COUNT(modes); ++i) {
            canvas->save();
            do_draw(canvas, modes[i], nullptr);
            canvas->translate(240, 0);
            do_draw(canvas, modes[i], imf);
            canvas->restore();
            
            canvas->translate(0, 240);
        }
}