Android中使用Bitmap类将矩形图片转为圆形的方法

时间:2022-02-18 18:31:04

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:

Android中使用Bitmap类将矩形图片转为圆形的方法

变成正圆后:

Android中使用Bitmap类将矩形图片转为圆形的方法

下面上代码:

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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:

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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;
}