通过RenderScript 实现 NV21转Bitmap、两张Bitmap按照透明度混合的工具类

之前写的一篇文章中我通过提取bitmap的数组，然后通过位移运算提取两个数组的alpha值通过比例混合为一张新的图片，这样对于大图片来说会很卡。所以我在查阅资料后:

安卓开发手册 ScriptIntrinsicBlend

通过RenderScript使用GPU加速来获得非常好的转换效果，只要使用安卓自身提供的脚本工具类ScriptIntrinsicBlend，配置好参数和输入输出，还有混合模式，即可快速完成该任务。

4k×2k的两张Bitmap可以在我的手机上只要30ms就可以混合完成。下面贴出我写的工具类:

package com.meizu.argbinsertyuv;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.ImageFormat;
import android.graphics.Rect;
import android.graphics.YuvImage;
import android.renderscript.Allocation;
import android.renderscript.Element;
import android.renderscript.RenderScript;
import android.renderscript.ScriptIntrinsicBlend;
import android.renderscript.ScriptIntrinsicYuvToRGB;
import android.renderscript.Type;
import android.util.Log;

import java.io.OutputStream;

/**@author 陈杰柱**/
public class YuvUtil {
    private Context mContext;
    private RenderScript rs;

    private ScriptIntrinsicYuvToRGB mYuvToRgbIntrinsic;
    private ScriptIntrinsicBlend mScriptIntrinsicBlend;

    private Type.Builder mYuvType, mRgbaType;
    private Type.Builder mRgbType1, mRgbType2;

    private Allocation mYuvin, mYuvOut;
    private Allocation mARGBPic1, mARGBPic2;

    private Bitmap mBmpout;

    public YuvUtil(Context context) {
        this.mContext = context;
        rs = RenderScript.create(context);
        mYuvToRgbIntrinsic = ScriptIntrinsicYuvToRGB.create(rs, Element.U8_4(rs));
        mScriptIntrinsicBlend = ScriptIntrinsicBlend.create(rs, Element.RGBA_8888(rs));
    }

    /**nv21转bmp**/
    public Bitmap nv21ToBitmap(byte[] nv21, int width, int height) {
        long start = System.currentTimeMillis();
        if (mYuvType == null) {
            mYuvType = new Type.Builder(rs, Element.U8(rs)).setX(nv21.length);
            mYuvin = Allocation.createTyped(rs, mYuvType.create(), Allocation.USAGE_SCRIPT);
            mRgbaType = new Type.Builder(rs, Element.RGBA_8888(rs)).setX(width).setY(height);
            mYuvOut = Allocation.createTyped(rs, mRgbaType.create(), Allocation.USAGE_SCRIPT);
        }
        mYuvin.copyFrom(nv21);
        mYuvToRgbIntrinsic.setInput(mYuvin);
        mYuvToRgbIntrinsic.forEach(mYuvOut);
        if (mBmpout == null) {
            mBmpout = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        } else if (mBmpout.getWidth() != width || mBmpout.getHeight() != height) {
            mBmpout = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        }
        mYuvOut.copyTo(mBmpout);
        Log.i("cjztest", "nv21转bmp" + (System.currentTimeMillis() - start) + "ms");
        return mBmpout;

    }

    /**两个bmp按照透明度混合**/
    public Bitmap bitmapBlendBitmap(Bitmap bottom, Bitmap top) {
        long start = System.currentTimeMillis();
        if (mRgbType1 == null || mRgbType2 == null) {
            mRgbType1 = new Type.Builder(rs, Element.RGBA_8888(rs)).setX(top.getWidth()).setY(top.getHeight());
            mRgbType2 = new Type.Builder(rs, Element.RGBA_8888(rs)).setX(bottom.getWidth()).setY(bottom.getHeight());
            mARGBPic1 = Allocation.createTyped(rs, mRgbType1.create(), Allocation.USAGE_SCRIPT);
            mARGBPic2 = Allocation.createTyped(rs, mRgbType2.create(), Allocation.USAGE_SCRIPT);
        }
        mARGBPic1.copyFrom(top);
        mARGBPic2.copyFrom(bottom);
//        mScriptIntrinsicBlend.forEachAdd(mARGBPic1, mYuvOut);
//        mScriptIntrinsicBlend.forEachDstAtop(mARGBPic1, mARGBPic2);
//        mScriptIntrinsicBlend.forEachDstIn(mARGBPic1, mARGBPic2);
//        mScriptIntrinsicBlend.forEachDstOut(mARGBPic2, mARGBPic1);
        mScriptIntrinsicBlend.forEachDstOver(mARGBPic2, mARGBPic1);
        if (mBmpout == null) {
            mBmpout = Bitmap.createBitmap(top.getWidth(), top.getHeight(), Bitmap.Config.ARGB_8888);
        } else if (mBmpout.getWidth() != top.getWidth() || mBmpout.getHeight() != top.getHeight()) {
            mBmpout = Bitmap.createBitmap(top.getWidth(), top.getHeight(), Bitmap.Config.ARGB_8888);
        }
        mARGBPic1.copyTo(mBmpout);
        Log.i("cjztest", "两个bmp按照透明度混合使用的时间" + (System.currentTimeMillis() - start) + "ms");
        return mBmpout;
    }


    /**传统方法把YUV转jpg**/
    public void nv21ToBitmapDirectSave(byte[] nv21, int width, int height, OutputStream os) {
        YuvImage im = new YuvImage(nv21, ImageFormat.NV21, width, height, new int[]{width, width, width});
        im.compressToJpeg(new Rect(0, 0, width, height), 80, os);
    }
}

另外可以符合使用，例如如果你希望实现在NV21上混合一个同样宽高的bmp，可以这么使用，也就是NV21先变成BMP再混合:

Bitmap resultBmp = mYuvUtil.bitmapBlendBitmap(mYuvUtil.nv21ToBitmap(photoBuffer, width, height), waterMarkBmp);