Incorporating 16-Color Bitmap Images

Would uou like to incorporate your own 16-color bitmap images into your Pro-SiMPLE programs? Let's look at one of the ways in which it can be done.

A bitmap file consists of essentially two parts. The beginning of the file contains some header information which indicates the size of the picture, the number of bits per pixel, etc. (In a 16-color bitmap file the length of this header is 118 bytes.) Following the header is the actual picture data. (In a 16-color bitmap file the picture data consists of pairs of pixels packed one pair per byte.)

As an example of how you might incorporate a 16-color bitmap image, let's write a program that will display three copies of the 94x144 image of Woody Woodpecker that you see at the top of this page. (But first you will need to copy the image into the root directory of your hard drive. Simply right-click on the image and select: "Save Picture As...")

    Pro-SiMPLE
    graph on
    Do x=230,310,40
       plot woody (x, x/2, -1) @
    Loop

    Task plot woody (Int x, Int y, Int inv)
    Common Int z[]={0,4,2,6,1,5,3,7,8,12,10,14,9,13,11,15}
    Common Int xsize=94, ysize=144
    Int data
    command="read C:\\woody.bmp"
    Open g (command)
    skip (118) @
    Do yy=ysize-1,0
       Do xx=0,xsize-1,2
          Read binary g (data, 0)
          zz=z[data/16]; If (zz!=inv) Put pixel (x+xx, y+yy, zz)
          If (xx=xsize-1) Break
          zz=z[data%16]; If (zz!=inv) Put pixel (x+xx+1, y+yy, zz)
       Loop
       skip ((16384-(xsize+1)/2)%4) @
    Loop
    Close g

    Task skip (Int n)
    Do k=1,n,1
       Read binary g (0, 0)
    Loop

*(The color value of each pixel must first be converted into the corres-
ponding SiMPLE color. Hence the use of the z[] conversion array.)

When we run the program, we get three overlapping copies of the woody.bmp image:

Notice that each successive image was plotted onto the screen without regard for any prior images underneath it. But then also notice that the plotwoody task has a third calling parameter, inv , which allows you to specify an "invisible" color (i.e., one which doesn't get plotted). Since the gray background in woody.bmp is color #7, let's change the third calling parameter (in line three of the program) from -1 to 7: