支持圆形裁剪框，裁剪后生成圆形图案。
代码基于开源项目修改，github上项目链接：/shengge/android-crop
还是贴下效果图：
说一下圆形裁剪实现部分：
1.UI方面，自定义CircleHighlightView继承至HighlightView（原有的矩形裁剪框实现），直接看draw方法实现
@Overrideprotected void draw(Canvas canvas) {canvas.save();Path path = new Path();outlinePaint.setStrokeWidth( outlineWidth);if(!hasFocus()) {//没焦点是，直接画一个黑色的矩形框outlinePaint.setColor( Color.BLACK);canvas.drawRect( drawRect, outlinePaint);}else {Rect viewDrawingRect = new Rect();viewContext.getDrawingRect( viewDrawingRect);//已裁剪框drawRect，算出圆的半径float radius = (drawRect.right - drawRect.left) / 2;//添加一个圆形path.addCircle( drawRect.left + radius, drawRect.top + radius, radius, Direction.CW);outlinePaint.setColor( highlightColor);//裁剪画布，path之外的区域，以outsidePaint填充canvas.clipPath( path, Region.Op.DIFFERENCE);canvas.drawRect( viewDrawingRect, outsidePaint);canvas.restore();//绘制圆上高亮线，这里outlinePaint定义的Paint.Style.STROKE：表示只绘制几何图形的轮廓。canvas.drawPath( path, outlinePaint);//当modifyMode为grow时，绘制handles,也就是那四个小圆if(handleMode == HandleMode.Always || (handleMode == HandleMode.Changing && modifyMode == ModifyMode.Grow)) {drawHandles( canvas);}}}
这里就实现了画圆形裁剪框的操作。
2. 响应和处理用户触摸事件
1). 判断触摸点坐标与圆的位置
/*** 根据x,y坐标，计算其与圆的关系（圆上、圆内、圆外）* @param x* @param y* @return*/private int getHitOnCircle(float x, float y) {Rect r = computeLayout();int retval = GROW_NONE;final float hysteresis = 20F;int radius = (r.right - r.left) / 2;int centerX = r.left + radius;int centerY = r.top + radius;//判断触摸位置是否在圆上float ret = (x - centerX) * (x - centerX) + (y - centerY) * (y - centerY);double rRadius = Math.sqrt( ret);double gap = Math.abs( rRadius - radius);if(gap <= hysteresis) {// 圆上。这里由于是继承至HighlightView（绘制矩形框的）来处理，所以模拟返回了左右上下，而非纯圆上，亲测可用。你也可以自定义。if(x < centerX) {// leftretval |= GROW_LEFT_EDGE;}else {retval |= GROW_RIGHT_EDGE;}if(y < centerY) {// upretval |= GROW_TOP_EDGE;}else {retval |= GROW_BOTTOM_EDGE;}}else if(rRadius > radius) {// outsideretval = GROW_NONE;}else if(rRadius < radius) {// inside，圆内就执行moveretval = MOVE;}return retval;}
由于是继承至HighLightView(矩形框)来实现的，如果点（x,y）位置圆上，还需判断其它那个象限，对应矩形的上下左右位置。
2). 移动裁剪框
若上一步判断，触摸点在圆内，就会返回MOVE，并处理移动过程。// Grows the cropping rectangle by (dx, dy) in image spacevoid moveBy(float dx, float dy) {Rect invalRect = new Rect(drawRect);//移动cropRect.offset(dx, dy);// Put the cropping rectangle inside image rectanglecropRect.offset(Math.max(0, imageRect.left - cropRect.left),Math.max(0, imageRect.top - cropRect.top));cropRect.offset(Math.min(0, imageRect.right - cropRect.right),Math.min(0, imageRect.bottom - cropRect.bottom));drawRect = computeLayout();invalRect.union(drawRect);invalRect.inset(-(int) handleRadius, -(int) handleRadius);viewContext.invalidate(invalRect);}
移动裁剪框并保证其它image图片显示范围内。
3). 缩放裁剪框
此过程和上一步类似，将cropRect矩阵进行等比缩放即可，这里就细说了，详见代码：HighLightView.growBy(float dx, float dy)3.将裁剪图片保存为圆形
/*** @param bitmap src图片* @return*/public static Bitmap getCircleBitmap(Bitmap bitmap) {Bitmap output = Bitmap.createBitmap( bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);Canvas canvas = new Canvas( output);final int color = 0xff424242;final Paint paint = new Paint();final Rect rect = new Rect( 0, 0, bitmap.getWidth(), bitmap.getHeight());paint.setAntiAlias( true);paint.setFilterBitmap( true);paint.setDither( true);canvas.drawARGB( 0, 0, 0, 0);paint.setColor( color);//在画布上绘制一个圆canvas.drawCircle( bitmap.getWidth() / 2, bitmap.getHeight() / 2, bitmap.getWidth() / 2, paint);paint.setXfermode( new PorterDuffXfermode( Mode.SRC_IN));canvas.drawBitmap( bitmap, rect, rect, paint);return output;}
注意：将bitmap保存为file时，格式请选择png，不然会出现黑色背景。
鉴于水平有限，从小语文就没学好，描述比较凌乱，需要深入理解的请阅读 源代码。
附：另外一个很好开源项目/edmodo/cropper
