skia2/gm/lcdblendmodes.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.
 */


/*
 * Tests text rendering with LCD and the various blend modes.
 */

#include "SkCanvas.h"
#include "SkGradientShader.h"
#include "SkSurface.h"
#include "ToolUtils.h"
#include "gm.h"

namespace skiagm {

constexpr int kColWidth = 180;
constexpr int kNumCols = 4;
constexpr int kWidth = kColWidth * kNumCols;
constexpr int kHeight = 750;

static sk_sp<SkShader> make_shader(const SkRect& bounds) {
    const SkPoint pts[] = {
        { bounds.left(), bounds.top() },
        { bounds.right(), bounds.bottom() },
    };
    const SkColor colors[] = {
        SK_ColorRED, SK_ColorGREEN,
    };
    return SkGradientShader::MakeLinear(pts, colors, nullptr, SK_ARRAY_COUNT(colors),
                                        SkShader::kRepeat_TileMode);
}

class LcdBlendGM : public skiagm::GM {
public:
    LcdBlendGM() {
        const int kPointSize = 25;
        fTextHeight = SkIntToScalar(kPointSize);
    }

protected:
    SkString onShortName() override {
        return SkString("lcdblendmodes");
    }

    void onOnceBeforeDraw() override {
        fCheckerboard = ToolUtils::create_checkerboard_shader(SK_ColorBLACK, SK_ColorWHITE, 4);
    }

    SkISize onISize() override { return SkISize::Make(kWidth, kHeight); }

    void onDraw(SkCanvas* canvas) override {
        SkPaint p;
        p.setAntiAlias(false);
        p.setStyle(SkPaint::kFill_Style);
        p.setShader(fCheckerboard);
        SkRect r = SkRect::MakeWH(SkIntToScalar(kWidth), SkIntToScalar(kHeight));
        canvas->drawRect(r, p);

        SkImageInfo info = SkImageInfo::MakeN32Premul(kWidth, kHeight);
        auto        surface(ToolUtils::makeSurface(canvas, info));

        SkCanvas* surfCanvas = surface->getCanvas();
        this->drawColumn(surfCanvas, SK_ColorBLACK, SK_ColorWHITE, false);
        surfCanvas->translate(SkIntToScalar(kColWidth), 0);
        this->drawColumn(surfCanvas, SK_ColorWHITE, SK_ColorBLACK, false);
        surfCanvas->translate(SkIntToScalar(kColWidth), 0);
        this->drawColumn(surfCanvas, SK_ColorGREEN, SK_ColorMAGENTA, false);
        surfCanvas->translate(SkIntToScalar(kColWidth), 0);
        this->drawColumn(surfCanvas, SK_ColorCYAN, SK_ColorMAGENTA, true);

        SkPaint surfPaint;
        surfPaint.setBlendMode(SkBlendMode::kSrcOver);
        surface->draw(canvas, 0, 0, &surfPaint);
    }

    void drawColumn(SkCanvas* canvas, SkColor backgroundColor, SkColor textColor, bool useGrad) {
        const SkBlendMode gModes[] = {
            SkBlendMode::kClear,
            SkBlendMode::kSrc,
            SkBlendMode::kDst,
            SkBlendMode::kSrcOver,
            SkBlendMode::kDstOver,
            SkBlendMode::kSrcIn,
            SkBlendMode::kDstIn,
            SkBlendMode::kSrcOut,
            SkBlendMode::kDstOut,
            SkBlendMode::kSrcATop,
            SkBlendMode::kDstATop,
            SkBlendMode::kXor,
            SkBlendMode::kPlus,
            SkBlendMode::kModulate,
            SkBlendMode::kScreen,
            SkBlendMode::kOverlay,
            SkBlendMode::kDarken,
            SkBlendMode::kLighten,
            SkBlendMode::kColorDodge,
            SkBlendMode::kColorBurn,
            SkBlendMode::kHardLight,
            SkBlendMode::kSoftLight,
            SkBlendMode::kDifference,
            SkBlendMode::kExclusion,
            SkBlendMode::kMultiply,
            SkBlendMode::kHue,
            SkBlendMode::kSaturation,
            SkBlendMode::kColor,
            SkBlendMode::kLuminosity,
        };
        // Draw background rect
        SkPaint backgroundPaint;
        backgroundPaint.setColor(backgroundColor);
        canvas->drawRect(SkRect::MakeIWH(kColWidth, kHeight), backgroundPaint);
        SkScalar y = fTextHeight;
        for (size_t m = 0; m < SK_ARRAY_COUNT(gModes); m++) {
            SkPaint paint;
            paint.setColor(textColor);
            paint.setBlendMode(gModes[m]);
            SkFont font(ToolUtils::create_portable_typeface(), fTextHeight);
            font.setSubpixel(true);
            font.setEdging(SkFont::Edging::kSubpixelAntiAlias);
            if (useGrad) {
                SkRect r;
                r.setXYWH(0, y - fTextHeight, SkIntToScalar(kColWidth), fTextHeight);
                paint.setShader(make_shader(r));
            }
            SkString string(SkBlendMode_Name(gModes[m]));
            canvas->drawString(string, 0, y, font, paint);
            y+=fTextHeight;
        }
    }

private:
    SkScalar fTextHeight;
    sk_sp<SkShader> fCheckerboard;
    typedef skiagm::GM INHERITED;
};

//////////////////////////////////////////////////////////////////////////////

DEF_GM( return new LcdBlendGM; )
}