The Trunk: Graphics-nice.290.mcz

Nicolas Cellier uploaded a new version of Graphics to project The Trunk:
http://source.squeak.org/trunk/Graphics-nice.290.mcz

==================== Summary ====================

Name: Graphics-nice.290
Author: nice
Time: 10 May 2014, 12:29:46.686 pm
UUID: 9d523439-e645-4632-a3b3-bb25c369b6fb
Ancestors: Graphics-nice.289

Fix reading of 16 bits per pixel PNG image with transparency.

=============== Diff against Graphics-nice.289 ===============

Item was changed:
  ----- Method: PNGReadWriter>>copyPixelsGray: (in category 'pixel copies') -----
  copyPixelsGray: y
  "Handle non-interlaced grayscale color mode (colorType = 0)"
 
  | base bits bytesLeft word |
  bitsPerChannel = 16 ifTrue: [
  "Warning: This is extremely slow. Besides we are downsampling to 8 bits!!"
  | blitter |
  blitter := BitBlt bitPokerToForm: form.
  0 to: width - 1 do: [ :x |
+ | high low value |
+ high := thisScanline at: x * 2 + 1.
+ low := thisScanline at: x * 2 + 2.
+ value := (high * 256 + low = transparentPixelValue)
+ ifTrue: [0 "transparent"]
+ ifFalse: [high max: 1].
+ blitter pixelAt: x @ y put: value ].
- blitter pixelAt: x @ y put: 255 - (thisScanline at: x * 2 + 1) ].
  ^self ].
 
  "Just copy the bits"
 
  "This Smalltalk version might be easier to understand than the others below."
  base := y * (form width * bitsPerChannel + 31 // 32) + 1.
  bits := form bits.
  0 to: thisScanline size // 4 - 1 do: [ :i |
  | ii |
  ii := i * 4.
  "This somewhat weird mixture of (#* and #+) with (#bitShift: and #bitOr:)
  is to make use of faster arithmetic bytecodes, but not of slow largeintegers."
  word :=
  (((thisScanline at: ii + 1) * 256 +
  (thisScanline at: ii + 2) * 256 +
  (thisScanline at: ii + 3)) bitShift: 8) bitOr:
  (thisScanline at: ii + 4).
  bits at: base + i put: word ].
  (bytesLeft := thisScanline size bitAnd: 3) = 0 ifFalse: [
  word := 0.
  thisScanline size - bytesLeft + 1 to: thisScanline size do: [ :ii |
  word := word * 256 + (thisScanline at: ii) ].
  word := word bitShift: 8 * (4 - bytesLeft).
  bits at: base + (thisScanline size // 4) put: word ].
 
  "This interesting technique (By Andreas Raab) is faster for very large images, but might be slower for small ones"
  "^self copyPixelsGrayWeirdBitBltHack: y ".
  "It uses the following method:
  PNGReadWriter >> copyPixelsGrayWeirdBitBltHack: y
  ""Handle non-interlaced black and white color mode (colorType = 0)
  By Andreas Raab""
 
  | source dest cmap |
  source := Form extent: 1 @ (thisScanline size // 4) depth: 32 bits: thisScanline.
  dest := Form extent: 1 @ (form bits size) depth: 32 bits: form bits.
  cmap := Smalltalk isLittleEndian
  ifTrue:[ColorMap
  shifts: #(-24 -8 8 24)
  masks: #(16rFF000000 16r00FF0000 16r0000FF00 16r000000FF)].
  (BitBlt toForm: dest)
  sourceForm: source;
  destX: 0 destY: (y * form width*bitsPerChannel//32) width: 1 height: (form width+31*bitsPerChannel//32);
  colorMap: cmap;
  combinationRule: 3;
  copyBits."
 
  "This interesting technique  (By Yoshiki Ohshima) is faster for very large images, but might be slower for small ones"
  "form bits copyFromByteArray2: thisScanline to: y * (form width* bitsPerChannel // 32)".
  "It uses the following method:
  BitMap >> copyFromByteArray2: byteArray to: i
  ""This method should work with either byte orderings""
 
  | myHack byteHack |
  myHack := Form new hackBits: self.
  byteHack := Form new hackBits: byteArray.
  Smalltalk  isLittleEndian ifTrue: [byteHack swapEndianness].
  byteHack displayOn: myHack at:  0@i"!

Item was changed:
  ----- Method: PNGReadWriter>>processTransparencyChunk (in category 'chunks') -----
  processTransparencyChunk
 
  | red green blue |
 
  "Transcript show: '  TRANSPARENCY ',chunk printString."
  colorType = 0 ifTrue: [
  transparentPixelValue := chunk unsignedShortAt: 1 bigEndian: true.
+ bitsPerChannel <= 8
+ ifTrue: [palette at: transparentPixelValue + 1 put: Color transparent]
+ ifFalse: [palette at: 1 put: Color transparent].
- palette at: transparentPixelValue put: Color transparent.
  ^self
  ].
  colorType = 2 ifTrue: [
  red := chunk at: 2.
  green := chunk at: 2.
  blue := chunk at: 2.
  transparentPixelValue := 16rFF00 + red << 8 + green << 8 + blue.
  ^self
  ].
  colorType = 3 ifTrue: [
  chunk withIndexDo: [ :alpha :index |
  palette at: index put: ((palette at: index) alpha: alpha/255)
  ].
  ^self
  ].
  !