将OpenGL ES 2.0渲染的纹理转换为位图再转换回去

Question

我希望使用RenderScript来模糊渲染纹理，因此需要将其转换为位图格式，并且在使用它之前需要将其转换回OpenGL纹理。

渲染到纹理是有效的。问题可能出在这里，但我不明白为什么它不起作用。屏幕是黑色的。

  public void renderToTexture(){
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, fb[0]);
    GLES20.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
    GLES20.glClear( GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);

    // specify texture as color attachment
    GLES20.glFramebufferTexture2D(GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0, GLES20.GL_TEXTURE_2D, renderTex[0], 0);
    // attach render buffer as depth buffer
    GLES20.glFramebufferRenderbuffer(GLES20.GL_FRAMEBUFFER, GLES20.GL_DEPTH_ATTACHMENT, GLES20.GL_RENDERBUFFER, depthRb[0]);
    // check status
    int status = GLES20.glCheckFramebufferStatus(GLES20.GL_FRAMEBUFFER);
    drawRender();

   Bitmap bitmap = SavePixels(0,0,texW,texH);
   //blur bitmap and get back a bluredBitmap not yet implemented
   texture = TextureHelper.loadTexture(bluredBitmap, 128);

   GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
   GLES20.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
   GLES20.glClear( GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);

    GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texture);

    drawRender2();

}

为了创建位图，我从帧缓冲区中读取像素，因为我没有找到其他方法，但我愿意接受其他方法。

    public static Bitmap SavePixels(int x, int y, int w, int h)
{
    int b[]=new int[w*(y+h)];
    int bt[]=new int[w*h];
    IntBuffer ib=IntBuffer.wrap(b);
    ib.position(0);
    GLES20.glReadPixels(0, 0, w, h, GLES20.GL_RGB, GLES20.GL_UNSIGNED_BYTE, ib);

    for(int i=0, k=0; i<h; i++, k++)
    {          
        for(int j=0; j<w; j++)
        {
            int pix=b[i*w+j];
            int pb=(pix>>16)&0xff;
            int pr=(pix<<16)&0x00ff0000;
            int pix1=(pix&0xff00ff00) | pr | pb;
            bt[(h-k-1)*w+j]=pix1;
        }
    }


    Bitmap sb=Bitmap.createBitmap(bt, w, h, Bitmap.Config.ARGB_8888);
    return sb;
}

以下是位图到纹理的代码：

    public static int loadTexture(final Bitmap pics, int size)
{
    final int[] textureHandle = new int[1];

    GLES20.glGenTextures(1, textureHandle, 0);

    if (textureHandle[0] != 0)
    {
        // Read in the resource
        final Bitmap bitmap = pics;

        GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA);
        GLES20.glEnable(GLES20.GL_BLEND);

        // Bind to the texture in OpenGL
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);

        // Set filtering
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);

        // Load the bitmap into the bound texture.
         GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);

        // Recycle the bitmap, since its data has been loaded into OpenGL.
        bitmap.recycle();
    }

    if (textureHandle[0] == 0)
    {
        throw new RuntimeException("Error loading texture.");
    }

    return textureHandle[0];
}

- FaNaT

Answer 1

你可以查看Android MediaCodec stuff，也可以直接查看ExtractMpegFramesTest_egl14.java，以下是代码片段：

    [/**
     * Saves][1] the current frame to disk as a PNG image.
     */
    public void saveFrame(String filename) throws IOException {
        // glReadPixels gives us a ByteBuffer filled with what is essentially big-endian RGBA
        // data (i.e. a byte of red, followed by a byte of green...).  To use the Bitmap
        // constructor that takes an int[] array with pixel data, we need an int[] filled
        // with little-endian ARGB data.
        //
        // If we implement this as a series of buf.get() calls, we can spend 2.5 seconds just
        // copying data around for a 720p frame.  It's better to do a bulk get() and then
        // rearrange the data in memory.  (For comparison, the PNG compress takes about 500ms
        // for a trivial frame.)
        //
        // So... we set the ByteBuffer to little-endian, which should turn the bulk IntBuffer
        // get() into a straight memcpy on most Android devices.  Our ints will hold ABGR data.
        // Swapping B and R gives us ARGB.  We need about 30ms for the bulk get(), and another
        // 270ms for the color swap.
        //
        // We can avoid the costly B/R swap here if we do it in the fragment shader (see
        // https://dev59.com/Knzaa4cB1Zd3GeqPNT7U ).
        //
        // Having said all that... it turns out that the Bitmap#copyPixelsFromBuffer()
        // method wants RGBA pixels, not ARGB, so if we create an empty bitmap and then
        // copy pixel data in we can avoid the swap issue entirely, and just copy straight
        // into the Bitmap from the ByteBuffer.
        //
        // Making this even more interesting is the upside-down nature of GL, which means
        // our output will look upside-down relative to what appears on screen if the
        // typical GL conventions are used.  (For ExtractMpegFrameTest, we avoid the issue
        // by inverting the frame when we render it.)
        //
        // Allocating large buffers is expensive, so we really want mPixelBuf to be
        // allocated ahead of time if possible.  We still get some allocations from the
        // Bitmap / PNG creation.

        mPixelBuf.rewind();
        GLES20.glReadPixels(0, 0, mWidth, mHeight, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE,
            mPixelBuf);

        BufferedOutputStream bos = null;
        try {
            bos = new BufferedOutputStream(new FileOutputStream(filename));
            Bitmap bmp = Bitmap.createBitmap(mWidth, mHeight, Bitmap.Config.ARGB_8888);
            mPixelBuf.rewind();
            bmp.copyPixelsFromBuffer(mPixelBuf);
            bmp.compress(Bitmap.CompressFormat.PNG, 90, bos);
            bmp.recycle();
        } finally {
            if (bos != null) bos.close();
        }
        if (VERBOSE) {
            Log.d(TAG, "Saved " + mWidth + "x" + mHeight + " frame as '" + filename + "'");
        }
    }

- Iven Zhang

Answer 2

你应该使用：

GLES20.glReadPixels(0, 0, w, h, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, ib);

你的for循环应该将RGBA转换为ARGB_8888

- Endre Börcsök