Bitmap数据处理

把直角图片改为圆角，通过改roundPx这个参数

fun toRoundBitmap(bitmap: Bitmap): Bitmap? {
  var width = bitmap.width
  var height = bitmap.height
  val roundPx: Float
  val left: Float
  val top: Float
  val right: Float
  val bottom: Float
  val dst_left: Float
  val dst_top: Float
  val dst_right: Float
  val dst_bottom: Float
  if (width <= height) {
    roundPx = width / 2.toFloat()
    left = 0f
    top = 0f
    right = width.toFloat()
    bottom = width.toFloat()
    height = width
    dst_left = 0f
    dst_top = 0f
    dst_right = width.toFloat()
    dst_bottom = width.toFloat()
  } else {
    roundPx = height / 2.toFloat()
    val clip = (width - height) / 2.toFloat()
    left = clip
    right = width - clip
    top = 0f
    bottom = height.toFloat()
    width = height
    dst_left = 0f
    dst_top = 0f
    dst_right = height.toFloat()
    dst_bottom = height.toFloat()
  }
  val output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
  val canvas = Canvas(output)
  val color = -0xbdbdbe
  val paint = Paint()
  val src = Rect(left.toInt(), top.toInt(), right.toInt(), bottom.toInt())
  val dst = Rect(dst_left.toInt(), dst_top.toInt(), dst_right.toInt(), dst_bottom.toInt())
  val rectF = RectF(dst)
  paint.isAntiAlias = true // 设置画笔无锯齿
  canvas.drawARGB(0, 0, 0, 0) // 填充整个Canvas
  paint.color = color

  // 以下有两种方法画圆,drawRounRect和drawCircle
  // canvas.drawRoundRect(rectF, roundPx, roundPx, paint);// 画圆角矩形，第一个参数为图形显示区域，第二个参数和第三个参数分别是水平圆角半径和垂直圆角半径。
  canvas.drawCircle(roundPx, roundPx, roundPx, paint)
  paint.xfermode = PorterDuffXfermode(PorterDuff.Mode.SRC_IN) // 设置两张图片相交时的模式,参考http://trylovecatch.iteye.com/blog/1189452
  canvas.drawBitmap(bitmap, src, dst, paint) //以Mode.SRC_IN模式合并bitmap和已经draw了的Circle
  return output
}