把图片转换成圆形图片

调用：（bt是Bitmap）

head_portrait.setImageBitmap(ToRoundBitmap.toRoundBitmap(bt));

转换圆形的方法：

package com.ghp.tools;

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.Bitmap.Config;

public class ToRoundBitmap {
    /**
     * 转成圆形图片
     * 
     * @param bitmap
     * @return
     */
    public static Bitmap toRoundBitmap(Bitmap bitmap) {
        int width = bitmap.getWidth();
        int height = bitmap.getHeight();

        final int color = Color.parseColor("#00FF00");
        // defaultWidth = width;
        // defaultHeight = height;

        float roundPx;
        float left, top, right, bottom, dst_left, dst_top, dst_right, dst_bottom;
        if (width <= height) { // 高大于宽
            roundPx = width / 2;
            left = 0;
            top = 0;
            right = width;
            bottom = width;
            height = width;
            dst_left = 0;
            dst_top = 0;
            dst_right = width;
            dst_bottom = width;
        } else { // 宽大于高
            roundPx = height / 2;
            float clip = (width - height) / 2;
            left = clip;
            right = width - clip;
            top = 0;
            bottom = height;
            width = height;
            dst_left = 0;
            dst_top = 0;
            dst_right = height;
            dst_bottom = height;
        }

        Bitmap output = Bitmap.createBitmap(width, height, Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final Paint paint = new Paint();
        paint.setAntiAlias(true);// 设置画笔无锯齿

        final Rect src = new Rect((int) left, (int) top, (int) right,
                (int) bottom);
        final Rect dst = new Rect((int) dst_left, (int) dst_top,
                (int) dst_right, (int) dst_bottom);
        canvas.drawARGB(0, 0, 0, 0); // 填充整个Canvas
        paint.setColor(color);
        paint.setDither(true);

        canvas.drawCircle(roundPx, roundPx, roundPx, paint);// 画圆
        paint.setXfermode(new PorterDuffXfermode(
                android.graphics.PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, src, dst, paint); // 以Mode.SRC_IN模式合并bitmap和已经draw了的Circle

        return output;
    }
}