PIX FMT RGBA
PIX_FMT_RGBA is a pixel format where 4 bytes are stored per pixel, one pixel for each of R, G, and B (red, green and blue) and one pixel for the alpha channel. The alpha channel allows transparency information to be stored per pixel.
Example 4 pixels will be stored as: RGBA RGBA RGBA RGBA.
4 pixels will take 4 * 4bpp (bytes per pixel) = 16 bytes of storage (uncompressed).