APNG_BLEND_OP_OVER      Blend previous frame into alpha
APNG_BLEND_OP_SOURCE    Completely replace the previous frame
APNG_DISPOSE_OP_BACKGROUND
                        Prepare region as fully transparent
APNG_DISPOSE_OP_NONE    Write over the current output buffer
APNG_DISPOSE_OP_PREVIOUS
                        Keep previous frame in rendering region
apng                    Convert static pngs to animated png
apng-package            Convert Png Files into Animated Png
