The Trunk: Graphics-nice.291.mcz

Nicolas Cellier uploaded a new version of Graphics to project The Trunk:
http://source.squeak.org/trunk/Graphics-nice.291.mcz

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

Name: Graphics-nice.291
Author: nice
Time: 10 May 2014, 1:58:27.633 pm
UUID: 3eb6e0ba-0411-4a77-9208-c231babaf2d0
Ancestors: Graphics-nice.290

Also handle transparency of 16 bits per channel interlaced gray scale PNG.

=============== Diff against Graphics-nice.290 ===============

Item was changed:
  ----- Method: PNGReadWriter>>copyPixelsGray:at:by: (in category 'pixel copies') -----
  copyPixelsGray: y at: startX by: incX
  "Handle interlaced grayscale color mode (colorType = 0)"
 
  | offset bits blitter pixPerByte shifts b pixel mask pixelNumber |
  bitsPerChannel = 16
  ifTrue: [
+ "Warning: This is extremely slow. Besides we are downsampling to 8 bits!!"
+ blitter := BitBlt bitPokerToForm: form.
- b := BitBlt bitPokerToForm: form.
  startX to: width-1 by: incX do: [ :x |
+ | high low value |
+ high := thisScanline at: x//incX<<1 + 1.
+ low := thisScanline at: x//incX<<1 + 2.
+ value := (high * 256 + low = transparentPixelValue)
+ ifTrue: [0 "transparent"]
+ ifFalse: [high max: 1].
+ blitter pixelAt: x @ y put: value ].
+ ^self ].
- b pixelAt: x@y put: 255 - (thisScanline at: (x//incX<<1)+1).
- ].
- ^ self
- ].
  offset := y*rowSize+1.
  bits := form bits.
  bitsPerChannel = 8 ifTrue: [
  startX to: width-1 by: incX do: [ :x | | w |
  w := offset + (x>>2).
  b := 3- (x \\ 4) * 8.
  pixel := (thisScanline at: x // incX + 1)<<b.
  mask := (255<<b) bitInvert32.
  bits at: w put: (((bits at: w) bitAnd: mask) bitOr: pixel)
  ].
  ^ self
  ].
  bitsPerChannel = 1 ifTrue: [
  pixPerByte := 8.
  mask := 1.
  shifts := #(7 6 5 4 3 2 1 0).
  ].
  bitsPerChannel = 2 ifTrue: [
  pixPerByte := 4.
  mask := 3.
  shifts := #(6 4 2 0).
  ].
  bitsPerChannel = 4 ifTrue: [
  pixPerByte := 2.
  mask := 15.
  shifts := #(4 0).
  ].
 
  blitter := BitBlt bitPokerToForm: form.
  pixelNumber := 0.
  startX to: width-1 by: incX do: [ :x | | rawByte |
  rawByte := thisScanline at: (pixelNumber // pixPerByte) + 1.
  pixel := (rawByte >> (shifts at: (pixelNumber \\ pixPerByte) + 1)) bitAnd: mask.
  blitter pixelAt: (x@y) put: pixel.
  pixelNumber := pixelNumber + 1.
  ].
  !