实现圆形图片-蒲公英云

实现圆形图片

SouthEast

实现原理：

得到原图的宽高，计算出圆心，取图片的短边为基准半径。
创建空白Bitmap，大小为基准半径的正方形。
位移原图，使其中心点和创建的空白图中心点重合。
利用Android的Paint绘制叠加图，只绘制重叠部分

效果完成。

public class CircleImageView extends ImageView{

public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}
public CircleImageView(Context context, AttributeSet attrs) {
    super(context, attrs);
}
public CircleImageView(Context context) {
    super(context);
}
@Override
public void setBackgroundDrawable(Drawable background) {
    super.setBackgroundDrawable(getCircleDrawable(getResources(), background));
}
@Override
public void setBackgroundResource(int resid) {
    //Don't worry, we don't need to override it,because it will be call 
    //setBackgroundDrawable(Drawable background)
    super.setBackgroundResource(resid);
}
@Override
public void setImageBitmap(Bitmap bm) {
    //Don't worry, we don't need to override it,because it will be call 
    //setImageDrawable(Drawable drawable)
    super.setImageBitmap(bm);
}
@Override
public void setImageDrawable(Drawable drawable) {
    super.setImageDrawable(getCircleDrawable(getResources(), drawable));
}
@Override
public void setImageURI(Uri uri) {
  //cheat it, let's change the way to implement
    super.setImageURI(uri);
    Drawable img = getCircleDrawable(getResources(), getDrawable());
    super.setImageDrawable(img);
}
@Override
public void setImageResource(int resId) {
    //cheat it, let's change the way to implement
    Drawable img = getCircleDrawable(getResources(), resId);
    super.setImageDrawable(img);
}
private static final int SPACING_LINE = 2;
private static Paint mCirclePaint = null;
private static Paint mLinePaint = null;
private static Paint getCirclePaint(){
    if(mCirclePaint == null){
        mCirclePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    }
    return mCirclePaint;
}
private static Paint getLinePaint(){
    if(mLinePaint == null){
        mLinePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mLinePaint.setStyle(Style.STROKE);
        //You can use it to change the width of the line
        mLinePaint.setStrokeWidth(1);
        //You can use it to change the color of the line
        mLinePaint.setColor(Color.BLACK);
    }
    return mLinePaint;
}
/** * You can call this method to generate the circular bitmap, * even if you don't use this class */
public static Bitmap getCircleBitmap(Bitmap src){
    if(src == null){
        return null;
    }
    int width  = src.getWidth();
    int height = src.getHeight();
    int centerX = width / 2;
    int centerY = height / 2;
    int radius  = Math.min(centerX, centerY) / 2;
    Bitmap result = Bitmap.createBitmap(radius * 2, radius * 2, Config.ARGB_8888);
    Canvas canvas = new Canvas(result);
    canvas.drawCircle(radius, radius, radius - SPACING_LINE, getCirclePaint());
    getCirclePaint().setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
    canvas.drawBitmap(src, -(centerX - radius), -(centerY - radius), getCirclePaint());
    //outer 
    canvas.drawCircle(radius, radius, radius, getLinePaint());
    //inner
    canvas.drawCircle(radius, radius, radius - SPACING_LINE, getLinePaint());
    //reset
    getCirclePaint().setXfermode(null);
    //recycle
    src.recycle();
    return result;
}
public static Bitmap getCircleBitmap(Drawable src){
    if(src instanceof BitmapDrawable){
        return getCircleBitmap(((BitmapDrawable)src).getBitmap());
    }else{
        //now, i don't know how to do...
        throw new UnsupportedException("Unsupported");
    }
}
public static Bitmap getCircleBitmap(Resources res,int id){
    return getCircleBitmap(BitmapFactory.decodeResource(res, id));
}
public static Drawable getCircleDrawable(Resources res, Bitmap src){
    return new BitmapDrawable(res,getCircleBitmap(src));
}
public static Drawable getCircleDrawable(Resources res, Drawable src){
    return new BitmapDrawable(res,getCircleBitmap(src));
}
public static Drawable getCircleDrawable(Resources res, int id) {
    return new BitmapDrawable(res, getCircleBitmap(res, id));
}
static class UnsupportedException extends RuntimeException{        
    private static final long serialVersionUID = 1L;
    public UnsupportedException(String str){
        super(str);
    }
}