Picasso加载圆角图片

效果图：

Demo地址：http://download.csdn.net/download/baopengjian/9948840

1 目的：

对Picasso加载的图片进行处理，如实现圆角效果、裁剪效果等等

2. 原理

1）Picasso提供了一个加载前暴露对图片处理的方法transform() ,需要传入的参数为实现了Transformation的类

Picasso.with(context).load(stock.getUrl()).transform(new CropSquareTransformation()).into

2）利用Bitmap本身的API进行圆角处理，提供的工具类任意圆角都是可以的

3. 使用：

1）定义类实现Transformation接口

public static class CropSquareTransformation implements Transformation {

@Override public Bitmap transform(Bitmap source) {

int raduis = 20;

Bitmap output = BitmapFillet.fillet(source,raduis ,BitmapFillet.CORNER_TOP);

if(source !=null){

source.recycle();

}

return output;

}

@Override public String key() { return "roundcorner"; }

}

2） BitmapFillet.fillet是对Bitmap的处理

public class BitmapFillet {

public static final int CORNER_NONE = 0;

public static final int CORNER_TOP_LEFT = 1;

public static final int CORNER_TOP_RIGHT = 1 << 1;

public static final int CORNER_BOTTOM_LEFT = 1 << 2;

public static final int CORNER_BOTTOM_RIGHT = 1 << 3;

public static final int CORNER_ALL = CORNER_TOP_LEFT | CORNER_TOP_RIGHT | CORNER_BOTTOM_LEFT | CORNER_BOTTOM_RIGHT;

public static final int CORNER_TOP = CORNER_TOP_LEFT | CORNER_TOP_RIGHT;

public static final int CORNER_BOTTOM = CORNER_BOTTOM_LEFT | CORNER_BOTTOM_RIGHT;

public static final int CORNER_LEFT = CORNER_TOP_LEFT | CORNER_BOTTOM_LEFT;

public static final int CORNER_RIGHT = CORNER_TOP_RIGHT | CORNER_BOTTOM_RIGHT;

public static Bitmap fillet(Bitmap bitmap, int roundPx, int corners) {

try {

// 其原理就是：先建立一个与图片大小相同的透明的Bitmap画板

// 然后在画板上画出一个想要的形状的区域。

// 最后把源图片帖上。

final int width = bitmap.getWidth();

final int height = bitmap.getHeight();

Bitmap paintingBoard = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

Canvas canvas = new Canvas(paintingBoard);

canvas.drawARGB(Color.TRANSPARENT, Color.TRANSPARENT, Color.TRANSPARENT, Color.TRANSPARENT);

final Paint paint = new Paint();

paint.setAntiAlias(true);

paint.setColor(Color.BLACK);

//画出4个圆角

final RectF rectF = new RectF(0, 0, width, height);

canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

//把不需要的圆角去掉

int notRoundedCorners = corners ^ CORNER_ALL;

if ((notRoundedCorners & CORNER_TOP_LEFT) != 0) {

clipTopLeft(canvas,paint,roundPx,width,height);

}

if ((notRoundedCorners & CORNER_TOP_RIGHT) != 0) {

clipTopRight(canvas, paint, roundPx, width, height);

}

if ((notRoundedCorners & CORNER_BOTTOM_LEFT) != 0) {

clipBottomLeft(canvas,paint,roundPx,width,height);

}

if ((notRoundedCorners & CORNER_BOTTOM_RIGHT) != 0) {

clipBottomRight(canvas, paint, roundPx, width, height);

}

paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));

//帖子图

final Rect src = new Rect(0, 0, width, height);

final Rect dst = src;

canvas.drawBitmap(bitmap, src, dst, paint);

return paintingBoard;

} catch (Exception exp) {

return bitmap;

}

}

private static void clipTopLeft(final Canvas canvas, final Paint paint, int offset, int width, int height) {

final Rect block = new Rect(0, 0, offset, offset);

canvas.drawRect(block, paint);

}

private static void clipTopRight(final Canvas canvas, final Paint paint, int offset, int width, int height) {

final Rect block = new Rect(width - offset, 0, width, offset);

canvas.drawRect(block, paint);

}

private static void clipBottomLeft(final Canvas canvas, final Paint paint, int offset, int width, int height) {

final Rect block = new Rect(0, height - offset, offset, height);

canvas.drawRect(block, paint);

}

private static void clipBottomRight(final Canvas canvas, final Paint paint, int offset, int width, int height) {

final Rect block = new Rect(width - offset, height - offset, width, height);

canvas.drawRect(block, paint);

}

}

3）使用

Picasso.with(context).load(stock.getUrl()).transform(new CropSquareTransformation()).into(iv_top);