Android中使用Bitmap类将矩形图片转为圆形的方法

Z时代
2024-01-10
分类：综合

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; 
}