Android- convert ARGB_8888 bitmap to 3BYTE_BGR

Question

I get the pixel data of my ARGB_8888 bitmap by doing this:

public void getImagePixels(byte[] pixels, Bitmap image) {
    // calculate how many bytes our image consists of
    int bytes = image.getByteCount();

    ByteBuffer buffer = ByteBuffer.allocate(bytes); // Create a new buffer
    image.copyPixelsToBuffer(buffer); // Move the byte data to the buffer

    pixels = buffer.array(); // Get the underlying array containing the data.
}

But, I would like to convert this data, in which each pixel is stored on four bytes (ARGB), to where each pixel is stored on 3 bytes (BGR).
Any help is appreciated!

Answer 1

Disclaimer: There could be better/easier/faster ways of doing this, using the Android Bitmap API, but I'm not familiar with it. If you want to go down the direction you started, here's your code modified to convert 4 byte ARGB to 3 byte BGR

public byte[] getImagePixels(Bitmap image) {
    // calculate how many bytes our image consists of
    int bytes = image.getByteCount();

    ByteBuffer buffer = ByteBuffer.allocate(bytes); // Create a new buffer
    image.copyPixelsToBuffer(buffer); // Move the byte data to the buffer

    byte[] temp = buffer.array(); // Get the underlying array containing the data.

    byte[] pixels = new byte[(temp.length / 4) * 3]; // Allocate for 3 byte BGR

    // Copy pixels into place
    for (int i = 0; i < (temp.length / 4); i++) {
       pixels[i * 3] = temp[i * 4 + 3];     // B
       pixels[i * 3 + 1] = temp[i * 4 + 2]; // G
       pixels[i * 3 + 2] = temp[i * 4 + 1]; // R

       // Alpha is discarded
    }

    return pixels;
}