Android开发常用工具类之图像处理

生成圆形的Bitmap

传入任意形状的bitmap，输出圆形Bitmap供显示

public Bitmap createCircularBitmap(Bitmap input, int width, int height) {
        if (input == null)
            return null;

        final int inWidth = input.getWidth();
        final int inHeight = input.getHeight();
        final Bitmap output = Bitmap.createBitmap(width, height,
                Bitmap.Config.ARGB_8888);
        final Canvas canvas = new Canvas(output);
        final Paint paint = new Paint();
        paint.setShader(new BitmapShader(input, Shader.TileMode.CLAMP,
                Shader.TileMode.CLAMP));
        paint.setAntiAlias(true);
        final RectF srcRect = new RectF(0, 0, inWidth, inHeight);
        final RectF dstRect = new RectF(0, 0, width, height);
        final Matrix m = new Matrix();
        m.setRectToRect(srcRect, dstRect, Matrix.ScaleToFit.CENTER);
        canvas.setMatrix(m);
        canvas.drawCircle(inWidth / 2, inHeight / 2, inWidth / 2, paint);
        return output;
}
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效果图如下： 

图片缩放

public static Bitmap resizeBitmapByScale(Bitmap bitmap, float scale,
            boolean recycle) {
        int width = Math.round(bitmap.getWidth() * scale);
        int height = Math.round(bitmap.getHeight() * scale);
        if (width == bitmap.getWidth() && height == bitmap.getHeight())
            return bitmap;
        Bitmap target = Bitmap.createBitmap(width, height,
                Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(target);
        canvas.scale(scale, scale);
        Paint paint = new Paint(Paint.FILTER_BITMAP_FLAG | Paint.DITHER_FLAG);
        canvas.drawBitmap(bitmap, 0, 0, paint);
        if (recycle)
            bitmap.recycle();
        return target;
}
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效果图如下： 

图片旋转

传入角度值，输出旋转后的Bitmap供显示，这里角度值不能是360的整数倍,求余运算排除此种情况。

public static Bitmap rotateBitmap(Bitmap source, int rotation,
            boolean recycle) {
        if (rotation % 360 == 0 || source == null)
            return source;
        int w = source.getWidth();
        int h = source.getHeight();
        Matrix m = new Matrix();
        m.postRotate(rotation);
        Bitmap bitmap = Bitmap.createBitmap(source, 0, 0, w, h, m, true);
        if (recycle)
            source.recycle();
        return bitmap;
}
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效果图如下： 

Bitmap转字节数组

有时需要将Bitmap转字节数组方便传输或存储，可以采用以下代码片段。

/**
* @param bitmap bitmap输入源
* @param quality 压缩质量，取值范围在0～100之间，
* @return 包含Bitmap信息的byte数组
*/
public static byte[] compressToBytes(Bitmap bitmap, int quality) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream(65536);
        bitmap.compress(CompressFormat.JPEG, quality, baos);
        return baos.toByteArray();
}
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反之如果需要将存储了Bitmap信息的字节数组转成Bitmap则可以用BitmapFactory里面的decodeByteArray(byte[] data, int offset, int length, Options opts)方法。