Android 图片绘制成圆角图片

版权声明：未经博主同意切勿转载 https://blog.csdn.net/qq_32136827/article/details/84850129

import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Shader;

/**
 * author cowards
 * created on 2018\11\23 0023
 **/
public class BitmapUtil {

    /**
     * 利用BitmapShader绘制圆角图片
     *
     * @param bitmap    待处理图片
     * @param outWidth  结果图片宽度，一般为控件的宽度
     * @param outHeight 结果图片高度，一般为控件的高度
     * @param radius    圆角半径大小
     * @return 结果图片
     */
    public static Bitmap roundBitmapByShader(Bitmap bitmap, int outWidth, int outHeight, int radius) {
        if (bitmap == null) {
            throw new NullPointerException("Bitmap can't be null");
        }
        // 初始化缩放比
        float widthScale = outWidth * 1.0f / bitmap.getWidth();
        float heightScale = outHeight * 1.0f / bitmap.getHeight();
        Matrix matrix = new Matrix();
        matrix.setScale(widthScale, heightScale);
        // 初始化绘制纹理图
        BitmapShader bitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
        // 根据控件大小对纹理图进行拉伸缩放处理
        bitmapShader.setLocalMatrix(matrix);
        // 初始化目标bitmap
        Bitmap targetBitmap = Bitmap.createBitmap(outWidth, outHeight, Bitmap.Config.ARGB_8888);
        // 初始化目标画布
        Canvas targetCanvas = new Canvas(targetBitmap);
        // 初始化画笔
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setShader(bitmapShader);
        // 利用画笔将纹理图绘制到画布上面
        targetCanvas.drawRoundRect(new RectF(0, 0, outWidth, outWidth), radius, radius, paint);
        return targetBitmap;
    }
}