android 圆形地图 Android中使用Bitmap类将矩形图片转为圆形的方法

一般要做正圆形图片，只能是正方形的基础上才能实现，否则就变成椭圆了，下面说说如何使长方形的图片生成正圆形图片

废话不多说，没图没真相，先上图吧：

原图：

变成正圆后：

下面上代码：

public static Bitmap makeRoundCorner(Bitmap bitmap)

{

int width = bitmap.getWidth();

int height = bitmap.getHeight();

int left = 0, top = 0, right = width, bottom = height;

float roundPx = height/2;

if (width > height) {

left = (width - height)/2;

top = 0;

right = left + height;

bottom = height;

} else if (height > width) {

left = 0;

top = (height - width)/2;

right = width;

bottom = top + width;

roundPx = width/2;

}

ZLog.i(TAG, "ps:"+ left +", "+ top +", "+ right +", "+ bottom);

Bitmap output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

Canvas canvas = new Canvas(output);

int color = 0xff424242;

Paint paint = new Paint();

Rect rect = new Rect(left, top, right, bottom);

RectF rectF = new RectF(rect);

paint.setAntiAlias(true);

canvas.drawARGB(0, 0, 0, 0);

paint.setColor(color);

canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));

canvas.drawBitmap(bitmap, rect, rect, paint);

return output;

}

下面再解释下：

由于图片是长方形，所以图片的 宽、高 肯定会有一边要小于另一边，要生成正方形就已最小的一边为基准，再来裁切定位另一边的显示范围

至于圆角的半径则是正方形宽的一半，用过 CSS 的就知道，画圆很方便 border-radius设为 50% 就可以了，都是一个道理

android 的 UI 真是太繁琐了

矩形画个圆角的代码：

public static Bitmap makeRoundCorner(Bitmap bitmap, int px)

{

int width = bitmap.getWidth();

int height = bitmap.getHeight();

Bitmap output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

Canvas canvas = new Canvas(output);

int color = 0xff424242;

Paint paint = new Paint();

Rect rect = new Rect(0, 0, width, height);

RectF rectF = new RectF(rect);

paint.setAntiAlias(true);

canvas.drawARGB(0, 0, 0, 0);

paint.setColor(color);

canvas.drawRoundRect(rectF, px, px, paint);

paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));

canvas.drawBitmap(bitmap, rect, rect, paint);

return output;

}