Glide 加载圆角或圆形图片

Glide的基础使用网上有很多，请自行查阅。

圆角和圆形图片如果是本地或者已知的Bitmap，建议大家使用Android supportV4 包中的RoundedBitmapDrawable（后面有补充使用方法）.

先上效果图

具体思路如下
1、使用Glide的transform方法
2、继承BitmapTransformation实现以便传入transform参数
3、实现BitmapTransformation的一个抽象方法transform
4、通过BitmapShader绘制图片样式

圆形图片

public class GlideCircleTransform extends BitmapTransformation {

    private int radius = 20;

    public GlideCircleTransform(Context context) {
        super(context);
    }

    public GlideCircleTransform(BitmapPool bitmapPool) {
        super(bitmapPool);
    }

    @Override
    protected Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {
        return roundCrop(pool, toTransform, outWidth, outHeight);
    }

    private Bitmap roundCrop(BitmapPool pool, Bitmap source, int outWidth, int outHeight) {
        if (source == null) return null;

        int size = Math.min(source.getWidth(), source.getHeight());
        int x = (source.getWidth() - size) / 2;
        int y = (source.getHeight() - size) / 2;
        Bitmap squared = Bitmap.createBitmap(source, x, y, size, size);
        Bitmap result = pool.get(size, size, Bitmap.Config.ARGB_8888);
        if (result == null) {
            result = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);
        }
        Canvas canvas = new Canvas(result);
        Paint paint = new Paint();
        paint.setShader(new BitmapShader(squared, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP));
        paint.setAntiAlias(true);

        int radius = size / 2;
        canvas.drawCircle(radius, radius, radius, paint);
        return result;
    }

    @Override
    public String getId() {
        return getClass().getName();
    }
}

注意： 这里既然是我们自己做的绘制，就会有个问题就是ImageView的android:scaleType 属性可能会失效，尤其是android:scaleType="centerCrop"已经失效，因为我们是固定截取的一张图片正中心的位置，所以如果是正方形的图片自然不存在该问题。

圆角图片

  private Bitmap roundCrop(BitmapPool pool, Bitmap source) {
        if (source == null) return null;
        int width = source.getWidth();
        int height = source.getHeight();
        Bitmap result = pool.get(width, height, Bitmap.Config.ARGB_8888);
        if (result == null) {
            result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        }
        Canvas canvas = new Canvas(result);
        Paint paint = new Paint();
        paint.setShader(new BitmapShader(source, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP));
        paint.setAntiAlias(true);

        RectF rectF = new RectF(0f, 0f, width, height);
        canvas.drawRoundRect(rectF, radius, radius, paint);
        return result;
    }

补充： RoundedBitmapDrawable 使用

RoundedBitmapDrawable drawableA = RoundedBitmapDrawableFactory.create(getResources(), id2Bitmap(this, R.drawable.icon_avatar));
drawableA.setCircular(true);       //是否是圆形
rbA.setImageDrawable(drawableA);

RoundedBitmapDrawable drawableB = RoundedBitmapDrawableFactory.create(getResources(), id2Bitmap(this, R.drawable.icon_avatar));
drawableB.setCornerRadius(30L);    //圆角
rbB.setImageDrawable(drawableB);

RoundedBitmapDrawable drawableC = RoundedBitmapDrawableFactory.create(getResources(), id2Bitmap(this, R.drawable.icon_avatar));
drawableC.setCornerRadius(60L);    //圆角
rbC.setImageDrawable(drawableC);