基本用法： 
Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);
处理图像大小: 
Picasso.with(context)
  .load(url)
  .resize(50, 50)
  .centerCrop()
  .into(imageView)
自定义特效: 
public class CropSquareTransformation implements Transformation {
  @Override public 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 result = Bitmap.createBitmap(source, x, y, size, size);
    if (result != source) {
      source.recycle();
    }
    return result;
  }

  @Override public String key() { return "square()"; }
}
设置图片下载与错误标识： 
Picasso.with(context)
    .load(url)
    .placeholder(R.drawable.user_placeholder)
    .error(R.drawable.user_placeholder_error)
    .into(imageView);
支持Resources, assets, files, content providers are all supported 等图片方式 
Picasso.with(context).load(R.drawable.landing_screen).into(imageView1);
Picasso.with(context).load(new File("/images/oprah_bees.gif")).into(imageView2);
开启调试信息 
Picasso.with(context).setDebugging(true);
更多信息：picasso