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