The orientation issue when save the EGL surface to a file in Android grafika open source code

Question

I use the saveFrame method in grafika. But I found there is orientation issue.

The left one is from saveFrame and the right one is what i see.

The code as following:

/**
 * Saves the EGL surface to a file.
 * <p>
 * Expects that this object's EGL surface is current.
 */
public void saveFrame(File file) throws IOException {
    if (!mEglCore.isCurrent(mEGLSurface)) {
        throw new RuntimeException("Expected EGL context/surface is not current");
    }

    // glReadPixels fills in a "direct" ByteBuffer with what is essentially big-endian RGBA
    // data (i.e. a byte of red, followed by a byte of green...).  While the Bitmap
    // constructor that takes an int[] wants little-endian ARGB (blue/red swapped), the
    // Bitmap "copy pixels" method wants the same format GL provides.
    //
    // Ideally we'd have some way to re-use the ByteBuffer, especially if we're calling
    // here often.
    //
    // 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.

    String filename = file.toString();

    int width = getWidth();
    int height = getHeight();
    ByteBuffer buf = ByteBuffer.allocateDirect(width * height * 4);
    buf.order(ByteOrder.LITTLE_ENDIAN);
    GLES20.glReadPixels(0, 0, width, height,
            GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, buf);
    GlUtil.checkGlError("glReadPixels");
    buf.rewind();

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

So how to deal with the orientation issue ?

Answer 1

Using the following code to save the problem:

IntBuffer ib = IntBuffer.allocate(width * height);
IntBuffer ibt = IntBuffer.allocate(width * height);
gl.glReadPixels(0, 0, width, height, GL10.GL_RGBA, GL10.GL_UNSIGNED_BYTE, ib);

// Convert upside down mirror-reversed image to right-side up normal image.
for (int i = 0; i < height; i++) {
    for (int j = 0; j < width; j++) {
        ibt.put((height - i - 1) * width + j, ib.get(i * width + j));
    }
}

Bitmap bitmap = Bitmap.createBitmap(width, height,Bitmap.Config.ARGB_8888);
bitmap.copyPixelsFromBuffer(ibt);