Android的 - 从一个方形点阵切圆 [英] Android - Cut a circle from a square Bitmap

问题描述

我试图使用以下code

I am trying to cut a circle from a square bitmap using following code

        Canvas canvas=new Canvas(bitmapimg );
        int circleXCoord = bitmapimg .getWidth() / 2;
        int circleYCoord = bitmapimg .getHeight() / 2;
        int circleRadius = bitmapimg .getWidth() / 2;

        Rect rect = new Rect(circleXCoord - circleRadius, circleYCoord - circleRadius, circleXCoord + circleRadius, circleYCoord + circleRadius);

        int width = rect.width();
        int height = rect.height();

        Paint paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.BLUE);
        canvas.drawRect(rect, paint);
        canvas.drawBitmap(bitmapimg , rect, rect, paint);
        Path p = new Path();
        p.addCircle(circleXCoord, circleYCoord, width / 2F, Path.Direction.CW);
        canvas.clipPath(p, Region.Op.DIFFERENCE);
        canvas.drawColor(0, PorterDuff.Mode.CLEAR);

我们的想法是附加一个正方形（矩形）的位图以帆布再夹的圆形路径。清除出矩形和圆形之间的差异（使其透明）。

The idea is to attach a square (rectangular) bitmap to canvas and then clip a circular path. Clear out the difference between the rectangle and circle (make it transparent).

在code正常工作的安卓4.0，但是在Android 2.3.3的设备，不同的区域出现黑色而该透明。

The code works fine for Android 4, but on Android 2.3.3 device, the difference area is appearing black rather that transparent.

我失去了一些东西在这里或PorterDuff.Mode.CLEAR不支持姜饼？有没有更好的方式来减少来自Android的一个正方形的圆？

Am I missing something here or PorterDuff.Mode.CLEAR is not supported in gingerbread? Is there a better way to cut a circle from a square in Android?

推荐答案

好像PorterDuff.Mode.Clear为姜饼没有工作

Seems like PorterDuff.Mode.Clear did not work for gingerbread

解决（从方使用该code切圆）的问题

Solved the problem (cut circle from square using this code)

        Bitmap output = Bitmap.createBitmap(bitmapimg.getWidth(),
                bitmapimg.getHeight(), Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final int color = 0xff424242;
        final Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, bitmapimg.getWidth(),
                bitmapimg.getHeight());

        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        canvas.drawCircle(bitmapimg.getWidth() / 2,
                bitmapimg.getHeight() / 2, bitmapimg.getWidth() / 2, paint);
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        canvas.drawBitmap(bitmapimg, rect, rect, paint);
        return output;

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