Status: FixedWaitingToBePharoed
Owner:
[hidden email]
Labels: Milestone-1.3 Type-Squeak
New issue 3661 by
[hidden email]: fixed the calculation of base in
PNGReadWriter>>copyPixelsGray: (floor vs ceil)
http://code.google.com/p/pharo/issues/detail?id=3661Name: Graphics-ul.177
Author: ul
Time: 5 February 2011, 4:53:19.27 am
UUID: dfac9cf3-85a4-3c4b-9256-1c8214f36fe6
Ancestors: Graphics-nice.176
- fixed the calculation of base in PNGReadWriter>>copyPixelsGray: (floor vs
ceil)
=============== Diff against Graphics-nice.176 ===============
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 current bitPokerToForm: form.
0 to: width - 1 do: [ :x |
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.
- base := y * form width * bitsPerChannel // 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"!
Locked
