Time for action – transferring imageData

By setting the chosen image to be of the same width and height as the group that holds the puzzle pieces (that's where the 900 and 662 numbers came from), it becomes possible for us to transfer the matching rectangle of data from the full image to the puzzle piece in question. The following steps will guide you in transferring imageData:

  1. Open the card script again. Add the makepuzzle handler:
    on makepuzzle
  resetpuzzle
  put the number of images in group "pieces" into imagecount
  repeat with a = 1 to imagecount
    makepiece the short name of image a of group "pieces"
  end repeat
end makepuzzle
  2. The makepuzzle handler will go through each of the puzzle pieces and call another handler to do the transfer of data for that one piece. Here is the makepiece handler:
    on makepiece piecename
  put the width of image piecename into piecewidth
  put the height of image piecename into pieceheight
  put empty into tempimage
  put the left of image piecename - the left of group "pieces" into dx
  put the top of image piecename - the top of group "pieces" into dy
  repeat with y = 1 to pieceheight
    put ((y+dy-1) * puzzlewidth + dx)*4 into sourcestart
    put char sourcestart+1 to sourcestart+piecewidth*4 of originalimage after tempimage
  end repeat
  set the imageData of image piecename to tempimage
end makepiece
  3. In the earlier imageData tests, we were only interested in one pixel at a time, but here, we want lots of rows of data. The arithmetic, ((y+dy-1) * puzzlewidth…, and so on, quickly pull out a whole row of pixels at a time. These rows are built up into a new variable, tempimage, which is finally transferred into the actual puzzle piece.
  4. After the pieces have their rectangle of imageData, we then need to move the pieces into random places, making the game ready for the user to play. This is done with a scatter handler:
    on scatter
  repeat with a = 1 to the number of images in group "pieces"
    set the myloc of image a of group "pieces" to the loc of image a of group "pieces"
    put the short name of image a of group "pieces" into n
    if edgepiece(n) then
      set the loc of image a of group "pieces" to 40 + random(400),300 + random(400)
    else
      set the loc of image a of group "pieces" to 500 + random(500),300 + random(400)
    end if
  end repeat
end scatter
  5. The first thing that most jigsaw puzzle players do is they separate the straight-edged pieces. We can code things in a way so that their time is saved. We can employ a function that places the edge pieces away from the non-edge pieces. The edgepiece function (which is called from the preceding scatter handler) is this:
    function edgepiece pName
  return word 2 of pName = 1 or word 3 of pName = 1 or word 2 of pName = hcount or word 3 of pName = vcount
end edgepiece
  6. The name that we carefully set for each piece is checked to verify that the piece is either at the left, right, top, or bottom edge of the puzzle. In other words, it's a piece located at the outer edges of the puzzle. Scatter places the straight-edged pieces in the left half of the screen and the others in the right half of the screen, as shown here:
    Time for action – transferring imageData
  7. The start of the makepuzzle handler calls a resetpuzzle handler that is used to make sure that the pieces are back where they started, ready for a new picture to load. This is achieved when you use a property variable on each piece named myloc, which records the initial location of the piece. Here's the resetpuzzle handler:
    on resetpuzzle
  repeat with a = 1 to the number of images in group "pieces"
    if the myloc of image a of group "pieces" is not empty then
      set the loc of image a of group "pieces" to the myloc of image a of group "pieces"
    else
     set the myloc of image a of group "pieces" to the loc of image a of group "pieces"
    end if
  end repeat
end resetpuzzle
  8. You can see that if myloc is not already set, then the piece must be in its start position, and so, the resetpuzzle handler goes ahead and records that location in the myloc property.
  9. Uncomment the lines at step 17 of Time for Action - creating the pieces and choosing an image (makepuzzle and scatter lines) and try another test of the app. You should now be able to choose a picture and see it in the spread out puzzle pieces. Hopefully, you will see something like this:
    Time for action – transferring imageData

What just happened?

As mentioned in the preceding section, the right arithmetic made it relatively easy for us to extract a desired rectangle of imageData from a larger image, and store it in a smaller image that was the size of that rectangle. However, there's one bit of magic that wasn't pointed out, the puzzle kept its shape! Even though we had completely replaced imageData for the image, how did this happen? Setting imageData doesn't interfere with alphaData of the image. The PNGs that we imported kept their original alpha channel and so still had the same shape, but just a different image.

Adding interactivity

Our jigsaw puzzle is ready to be shipped! Well, other than the fact it has no interactivity at all! Let's add some.

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