# Bruce Maxwell
# Spring 2010

import sys
import graphics as gr
import filter

# main function
# creates a new image, puts the first image on the left and
# the second half-overlapping it with an alpha blend of 0.5
def main( argv ):
    if len(argv) < 3:
        print( 'Usage: testpixmap.py <ppm image 1> <ppm image 2>')
        print( '\n       Reads in the two images and builds a collage')
        print( '       with the second image overlapping the first ')
        print( '       using an alpha blend of 0.5')
        print( '\n       The output image is called blend.ppm')
        print("\n")
        exit()

    # read both images
    srcA = gr.Image( gr.Point(0,0), argv[1] )
    srcB = gr.Image( gr.Point(0,0), argv[2] )

    # get the maximum height of the two images
    rows = srcA.getHeight()
    if srcB.getHeight() > rows:
        rows = srcB.getHeight()

    # make the columns big enough
    cols = srcA.getWidth()//2 + srcB.getWidth()
    if srcA.getWidth() > cols:
        cols = srcA.getWidth()

    # create the background canvas
    dst = gr.Image( gr.Point(0,0), cols, rows )

    # put both images into the canvas
    filter.placeImage( dst, srcA, 0, 0, 1.0 )
    filter.placeImage( dst, srcB, srcA.getWidth()//2, 0, 0.5 )

    # write out the canvas
    print("Writing out image blend.ppm")
    dst.save( 'blend.ppm' )

    return

if __name__ == "__main__":
    main(sys.argv)