教你如何绘制圆形头像

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


/**
 * 绘制圆形图片的工具类
 * @author 990
 * 
 */
public class RoundnessBitmap {

/**
* 绘制圆形图片的方法
* 
* @param bitmap
* @return
*/
public static Bitmap canvasRoundImgv(Bitmap bitmap) {

int width = bitmap.getWidth();// 获取图片的宽度值
int height = bitmap.getHeight();// 获取图片的高度值

float roundPx;// 圆角半径值
float left, right, top, bottom, dst_left, dst_right, dst_top, dst_bottom;

if (width <= height) {
roundPx = width / 2;
top = 0;
left = 0;
bottom = width;
right = width;
height = width;
dst_left = 0;
dst_top = 0;
dst_right = width;
dst_bottom = width;
} else {
roundPx = height;
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);
// 绘制图片的画布
Canvas canvas = new Canvas(output);
// 获取画笔
Paint paint = new Paint();
// 绘制矩形
Rect src = new Rect((int) left, (int) top, (int) right, (int) bottom);// 前景
Rect dst = new Rect((int) dst_left, (int) dst_top, (int) dst_right,
(int) dst_bottom);// 原图

RectF rectf = new RectF(dst);

paint.setAntiAlias(true);// 设置抗锯齿
paint.setColor(Color.WHITE);
paint.setStrokeWidth(4);
canvas.drawARGB(0, 0, 0, 0);// 设置画布颜色值
/**
* 参数一：RectF对象。
* 参数二rx：x方向上的圆角半径。
* 参数三ry：y方向上的圆角半径。
* 参数四paint：绘制时所使用的画笔。
*/
canvas.drawRoundRect(rectf, roundPx, roundPx, paint);// 在画布上绘制圆角矩形，通过指定RectF对象以及圆角半径来实现
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));// 设置两张图片相交时的模式
canvas.drawBitmap(bitmap, src, dst, paint);

// 画白色圆圈
paint.reset();
paint.setColor(Color.WHITE);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(5);
paint.setAntiAlias(true);
canvas.drawCircle(width / 2, width / 2, width / 2 - 5 / 2, paint);

return output;
}
}