transparency.cpp File Reference

#include "gm/gm.h"
#include "include/core/SkBitmap.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkColor.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "include/core/SkShader.h"
#include "include/core/SkSurface.h"
#include "include/core/SkTileMode.h"
#include "include/core/SkTypes.h"
#include "include/effects/SkGradientShader.h"

Go to the source code of this file.

Functions
static void	make_transparency (SkCanvas *canvas, SkScalar width, SkScalar height)
static sk_sp< SkShader >	create_checkerboard_shader (SkColor c1, SkColor c2, int size)
static void	checkerboard (SkCanvas *canvas, SkColor c1, SkColor c2, int size)
	DEF_SIMPLE_GM (transparency_check, canvas, 1792, 1080)

Function Documentation

checkerboard()

static void checkerboard ( SkCanvas *  canvas, SkColor  c1, SkColor  c2, int  size  )

static

Definition at line 60 of file transparency.cpp.

                                                                             {
    SkPaint paint;
    paint.setShader(create_checkerboard_shader(c1, c2, size));
    canvas->drawPaint(paint);
}

create_checkerboard_shader()

static sk_sp< SkShader > create_checkerboard_shader ( SkColor  c1, SkColor  c2, int  size  )

static

Definition at line 50 of file transparency.cpp.

                                                                                    {
    SkBitmap bm;
    bm.allocN32Pixels(2 * size, 2 * size);
    bm.eraseColor(c1);
    bm.eraseArea(SkIRect::MakeLTRB(0, 0, size, size), c2);
    bm.eraseArea(SkIRect::MakeLTRB(size, size, 2 * size, 2 * size), c2);
    return bm.makeShader(SkTileMode::kRepeat, SkTileMode::kRepeat, SkSamplingOptions());
}

DEF_SIMPLE_GM()

DEF_SIMPLE_GM	(	transparency_check	,
		canvas	,
		1792	,
		1080
	)

This GM verifies that a transparent bitmap drawn over a checkerboard pattern looks correct.

Definition at line 70 of file transparency.cpp.

                                                      {
    checkerboard(canvas, 0xFF999999, 0xFF666666, 8);
    {
        SkAutoCanvasRestore autoCanvasRestore(canvas, true);
        auto surface(SkSurfaces::Raster(SkImageInfo::MakeN32Premul(256, 9)));
        make_transparency(surface->getCanvas(), 256.0f, 9.0f);
        canvas->scale(7.0f, 120.0f);
        surface->draw(canvas, 0, 0);
    }
}

make_transparency()

static void make_transparency ( SkCanvas *  canvas, SkScalar  width, SkScalar  height  )

static

Definition at line 23 of file transparency.cpp.

                                                                                 {
    SkPoint pts[2];
    pts[0] = SkPoint::Make(0, 0);
    pts[1] = SkPoint::Make(width, 0);
    const SkColor kColors[] = {
            SK_ColorBLACK,
            SK_ColorGRAY,
            SK_ColorWHITE,
            SK_ColorRED,
            SK_ColorYELLOW,
            SK_ColorGREEN,
            SK_ColorCYAN,
            SK_ColorBLUE,
            SK_ColorMAGENTA,
    };
    const SkScalar kRowHeight = height / std::size(kColors);
    for (size_t i = 0; i < std::size(kColors); ++i) {
        SkColor shaderColors[2];
        shaderColors[0] = SK_AlphaTRANSPARENT;
        shaderColors[1] = kColors[i];
        SkPaint p;
        p.setShader(SkGradientShader::MakeLinear(pts, shaderColors, nullptr, 2, SkTileMode::kClamp));
        canvas->drawRect(SkRect::MakeXYWH(0, i * kRowHeight, width, kRowHeight), p);
    }
}