squeak의 BitBlt(픽셀 이동) 가지고 놀기. 
참고. 
  * http://squeak.qp.land.to/wiki/index.php?BitBlt
  * Form method : Combination Rule

  * 이미지 alpha 값 조절: 크기가 같은 2개의 이미지(알파이미지, 원본이미지)를 합침
<code>
Display newDepth:32.

  | alphaBlit alphaForm |
alphaForm := Form extent: (ImageMorph new extent) depth: 32.
"alphaForm asMorph openInWorld." "test"
alphaForm fillColor: (Color r: 1.0 g: 1.0 b: 0.0 alpha: 0.3).
anImage := ImageMorph new imageForm.
alphaBlit := BitBlt
		destForm: anImage
		sourceForm: alphaForm
		fillColor: Color red "any Color but Color transparent"
		combinationRule: 4 "4번은 투명, Form erase"
		destOrigin: 0@0
		sourceOrigin: 0@0
		extent: (anImage extent)
		clipRect: (anImage boundingBox).
alphaBlit copyBits. "적용"
(SketchMorph withForm: anImage) openInWorld. 
</code>
  * 이미지에서 원하는 부분 추출.

  * 이미지 마스킹

----
WarpBlt 
 참고 http://www.ida.liu.se/~ETE257/timetable/LectureMorphic.html

<code>
| f warp r pts|
f := Form fromUser.
warp := (WarpBlt toForm: Display)
    cellSize: 1;
    sourceForm: f;
    cellSize: 2;  "installs a colormap"
    combinationRule: Form over.

r := (0@0) extent: f extent.
pts := {r topLeft. r bottomLeft. r bottomRight. r topRight}.

warp 
    copyQuad: pts 
    toRect: ((0@0) extent: (200@200)).
</code>