使用UIL的内置圆角图片的功能时，发现一个BUG，就是它会拉伸图片，造成图片失真。费了一下午的功夫，重写了RoundedBitmapDisplayer，总算解决这个问题。

代码如下：

public class RoundedBitmapDisplayer implements BitmapDisplayer {    protected final int cornerRadius;    protected final int margin;    public RoundedBitmapDisplayer(int cornerRadiusPixels) {        this(cornerRadiusPixels, 0);    }    public RoundedBitmapDisplayer(int cornerRadiusPixels, int marginPixels) {        this.cornerRadius = cornerRadiusPixels;        this.margin = marginPixels;    }    @Override    public void display(Bitmap bitmap, ImageAware imageAware, LoadedFrom loadedFrom) {        if (!(imageAware instanceof ImageViewAware)) {            throw new IllegalArgumentException("ImageAware should wrap ImageView. ImageViewAware is expected.");        }        imageAware.setImageDrawable(new RoundedDrawable(bitmap, cornerRadius, margin));    }    public static class RoundedDrawable extends Drawable {        protected final float cornerRadius;        protected final int margin;        protected final RectF mBorderRect = new RectF(), mBitmapRect;        protected final BitmapShader mBitmapShader;        protected final Paint paint;        private final Matrix mShaderMatrix = new Matrix();        private float scale = 1.0f, dx, dy;         private int mBitmapWidth, mBitmapHeight;        private int mBorderWidth = 0;        public RoundedDrawable(Bitmap bitmap, int cornerRadius, int margin) {            this.cornerRadius = cornerRadius;            this.margin = margin;            mBitmapWidth = bitmap.getWidth();            mBitmapHeight = bitmap.getHeight();            mBitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);            mBitmapRect = new RectF (margin, margin, bitmap.getWidth() - margin, bitmap.getHeight() - margin);                        paint = new Paint();            paint.setAntiAlias(true);            paint.setShader(mBitmapShader);            paint.setFilterBitmap(true);            paint.setDither(true);        }        @Override        protected void onBoundsChange(Rect bounds) {            super.onBoundsChange(bounds);            mBorderRect.set(margin, margin, bounds.width() - margin, bounds.height() - margin);                            mBorderRect.inset(mBorderWidth / 2, mBorderWidth / 2);            mShaderMatrix.reset();            dx = 0;            dy = 0;            if (mBitmapWidth * mBorderRect.height() > mBorderRect.width() * mBitmapHeight) {                scale = mBorderRect.height() / (float) mBitmapHeight;                dx = (mBorderRect.width() - mBitmapWidth * scale) * 0.5f;            } else {                scale = mBorderRect.width() / (float) mBitmapWidth;                dy = (mBorderRect.height() - mBitmapHeight * scale) * 0.5f;            }            mShaderMatrix.setScale(scale, scale);            mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth / 2, (int) (dy + 0.5f) + mBorderWidth / 2);            // 设置shader            mBitmapShader.setLocalMatrix(mShaderMatrix);        }        @Override        public void draw(Canvas canvas) {            canvas.drawRoundRect(mBorderRect, cornerRadius, cornerRadius, paint);        }        @Override        public int getOpacity() {            return PixelFormat.TRANSLUCENT;        }        @Override        public void setAlpha(int alpha) {            paint.setAlpha(alpha);        }        @Override        public void setColorFilter(ColorFilter cf) {            paint.setColorFilter(cf);        }    }}