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Diffstat (limited to 'Imaging/Tk/booster.txt')
| -rw-r--r-- | Imaging/Tk/booster.txt | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/Imaging/Tk/booster.txt b/Imaging/Tk/booster.txt new file mode 100644 index 0000000..2d78798 --- /dev/null +++ b/Imaging/Tk/booster.txt @@ -0,0 +1,108 @@ +==================================================================== +The Photoimage Booster Patch (for Windows 95/NT) +==================================================================== + + This patch kit boosts performance for 16/24-bit displays. The +first patch is required on Tk 4.2 (where it fixes the problems for +16-bit displays) and later versions, with the exception for Tk 8.0b1 +where Sun added something similar themselves, only to remove it in +8.0b2. By installing both patches, Tk's PhotoImage handling becomes +much faster on both 16-bit and 24-bit displays. The patch has been +tested with Tk 4.2 and 8.0. + + Here's a benchmark, made with a sample program which loads two +512x512 greyscale PGM's, and two 512x512 colour PPM's, and displays +each of them in a separate toplevel windows. Tcl/Tk was compiled +with Visual C 4.0, and run on a P100 under Win95. Image load times +are not included in the timings: + + 8-bit 16-bit 24-bit +-------------------------------------------------------------------- +1. original 4.2 code 5.52 s 8.57 s 3.79 s +2. booster patch 5.49 s 1.87 s 1.82 s + + speedup None 4.6x 2.1x + +==================================================================== + +Here's the patches: + +1. For portability and speed, the best thing under Windows is to +treat 16-bit displays as if they were 24-bit. The Windows device +drivers take care of the rest. + + ---------------------------------------------------------------- + If you have Tk 4.1 or Tk 8.0b1, you don't have to apply this + patch! It only applies to Tk 4.2, Tk 8.0a[12] and Tk 8.0b2. + ---------------------------------------------------------------- + +In win/tkWinImage.c, change the following line in XCreateImage: + + imagePtr->bits_per_pixel = depth; + +to + +/* ==================================================================== */ +/* The tk photo image booster patch -- patch section 1 */ +/* ==================================================================== */ + + if (visual->class == TrueColor) + /* true colour is stored as 3 bytes: (blue, green, red) */ + imagePtr->bits_per_pixel = 24; + else + imagePtr->bits_per_pixel = depth; + +/* ==================================================================== */ + + +2. The DitherInstance implementation is not good. It's especially +bad on highend truecolour displays. IMO, it should be rewritten from +scratch (some other day...). + + Anyway, the following band-aid makes the situation a little bit +better under Windows. This hack trades some marginal quality (no +dithering on 16-bit displays) for a dramatic performance boost. +Requires patch 1, unless you're using Tk 4.1 or Tk 8.0b1. + +In generic/tkImgPhoto.c, add the #ifdef section to the DitherInstance +function: + + for (; height > 0; height -= nLines) { + if (nLines > height) { + nLines = height; + } + dstLinePtr = (unsigned char *) imagePtr->data; + yEnd = yStart + nLines; + +/* ==================================================================== */ +/* The tk photo image booster patch -- patch section 2 */ +/* ==================================================================== */ + +#ifdef __WIN32__ + if (colorPtr->visualInfo.class == TrueColor + && instancePtr->gamma == 1.0) { + /* Windows hicolor/truecolor booster */ + for (y = yStart; y < yEnd; ++y) { + destBytePtr = dstLinePtr; + srcPtr = srcLinePtr; + for (x = xStart; x < xEnd; ++x) { + destBytePtr[0] = srcPtr[2]; + destBytePtr[1] = srcPtr[1]; + destBytePtr[2] = srcPtr[0]; + destBytePtr += 3; srcPtr += 3; + } + srcLinePtr += lineLength; + dstLinePtr += bytesPerLine; + } + } else +#endif + +/* ==================================================================== */ + + for (y = yStart; y < yEnd; ++y) { + srcPtr = srcLinePtr; + errPtr = errLinePtr; + destBytePtr = dstLinePtr; + +==================================================================== +last updated: 97-07-03/fl |