compile 'com.squareup.picasso:picasso:2.5.2'

Picasso.with(Activity.this).load(URL).transform(new CircleCornerForm()).error(R.drawable.head).into(ImageView);

import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Paint;import com.squareup.picasso.Transformation;/*** Created libin on 2016/4/25.* 圆形图片*/
public class CircleTransform implements Transformation {@Overridepublic Bitmap transform(Bitmap source) {int size = Math.min(source.getWidth(), source.getHeight());int x = (source.getWidth() - size) / 2;int y = (source.getHeight() - size) / 2;Bitmap squaredBitmap = Bitmap.createBitmap(source, x, y, size, size);if (squaredBitmap != source) {source.recycle();}Bitmap bitmap = Bitmap.createBitmap(size, size, source.getConfig());Canvas canvas = new Canvas(bitmap);Paint paint = new Paint();BitmapShader shader = new BitmapShader(squaredBitmap,BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP);paint.setShader(shader);paint.setAntiAlias(true);float r = size / 2f;canvas.drawCircle(r, r, r, paint);squaredBitmap.recycle();return bitmap;}@Overridepublic String key() {return "circle";}
}

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;import com.squareup.picasso.Transformation;/*** Created by libin on 16/7/22.* 圆角切片*/
public class CircleCornerForm implements Transformation {@Overridepublic Bitmap transform(Bitmap source) {int widthLight = source.getWidth();int heightLight = source.getHeight();Bitmap output = Bitmap.createBitmap(source.getWidth(), source.getHeight(), Bitmap.Config.ARGB_8888);Canvas canvas = new Canvas(output);Paint paintColor = new Paint();paintColor.setFlags(Paint.ANTI_ALIAS_FLAG);RectF rectF = new RectF(new Rect(0, 0, widthLight, heightLight));canvas.drawRoundRect(rectF, widthLight / 5, heightLight / 5, paintColor);//这里除的数越大角度越小Paint paintImage = new Paint();paintImage.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_ATOP));canvas.drawBitmap(source, 0, 0, paintImage);source.recycle();return output;}@Overridepublic String key() {return "roundcorner";}
}