Status: FixedWaitingToBePharoed Owner: stephane...@gmail.com Labels: Milestone-1.3 Type-Squeak New issue 3661 by stephane...@gmail.com: fixed the calculation of base in PNGReadWriter>>copyPixelsGray: (floor vs ceil) http://code.google.com/p/pharo/issues/detail?id=3661 Name: 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"!