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authordkf <donal.k.fellows@manchester.ac.uk>2007-10-31 10:24:08 (GMT)
committerdkf <donal.k.fellows@manchester.ac.uk>2007-10-31 10:24:08 (GMT)
commit8cff39c2e6ce28a548c13c2f71f991658686e7d1 (patch)
tree53d654c36c9a37987ba4d10a24bfd5dbd4f9404a /generic/tkImgPhoto.c
parent644cecc295e9fd371226e9c5b3eeeb50b0181b41 (diff)
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Improve Tk_PhotoPutBlock a bit more. Derived from [Patch 224066]
Diffstat (limited to 'generic/tkImgPhoto.c')
-rw-r--r--generic/tkImgPhoto.c78
1 files changed, 53 insertions, 25 deletions
diff --git a/generic/tkImgPhoto.c b/generic/tkImgPhoto.c
index 88d3603..a2e814a 100644
--- a/generic/tkImgPhoto.c
+++ b/generic/tkImgPhoto.c
@@ -17,7 +17,7 @@
* Department of Computer Science,
* Australian National University.
*
- * RCS: @(#) $Id: tkImgPhoto.c,v 1.74 2007/10/30 15:34:57 dkf Exp $
+ * RCS: @(#) $Id: tkImgPhoto.c,v 1.75 2007/10/31 10:24:09 dkf Exp $
*/
#include "tkInt.h"
@@ -4424,6 +4424,9 @@ Tk_PhotoPutBlock(
*/
for (hLeft = height; hLeft > 0;) {
+ int pixelSize = blockPtr->pixelSize;
+ int compRuleSet = (compRule == TK_PHOTO_COMPOSITE_SET);
+
srcLinePtr = blockPtr->pixelPtr + blockPtr->offset[0];
hCopy = MIN(hLeft, blockPtr->height);
hLeft -= hCopy;
@@ -4434,10 +4437,10 @@ Tk_PhotoPutBlock(
* much faster.
*/
- if ((blockPtr->pixelSize == 4) && (greenOffset == 1)
+ if ((pixelSize == 4) && (greenOffset == 1)
&& (blueOffset == 2) && (alphaOffset == 3)
&& (width <= blockPtr->width)
- && (compRule == TK_PHOTO_COMPOSITE_SET)) {
+ && compRuleSet) {
memcpy(destLinePtr, srcLinePtr, (size_t) (width * 4));
srcLinePtr += blockPtr->pitch;
destLinePtr += pitch;
@@ -4453,35 +4456,56 @@ Tk_PhotoPutBlock(
wCopy = MIN(wLeft, blockPtr->width);
wLeft -= wCopy;
srcPtr = srcLinePtr;
- for (; wCopy>0 ; --wCopy, srcPtr+=blockPtr->pixelSize) {
- int alpha = srcPtr[alphaOffset];
+ /*
+ * But we might be lucky and be able to use fairly fast loops.
+ * It's worth checking...
+ */
+
+ if (alphaOffset == 0) {
/*
- * In the easy case, we can just copy.
+ * This is the non-alpha case, so can still be fairly
+ * fast. Note that in the non-alpha-source case, the
+ * compositing rule doesn't apply.
*/
- if (!alphaOffset || (alpha == 255)) {
- /*
- * New solid part of the image.
- */
-
+ for (; wCopy>0 ; --wCopy, srcPtr+=pixelSize) {
*destPtr++ = srcPtr[0];
*destPtr++ = srcPtr[greenOffset];
*destPtr++ = srcPtr[blueOffset];
*destPtr++ = 255;
- continue;
}
-
+ continue;
+ } else if (compRuleSet) {
/*
- * Combine according to the compositing rule.
+ * This is the SET compositing rule, which just replaces
+ * what was there before with the new data. This is
+ * another fairly fast case. No point in doing a memcpy();
+ * the order of channels is probably wrong.
*/
- if ((compRule == TK_PHOTO_COMPOSITE_SET) || !destPtr[3]) {
+ for (; wCopy>0 ; --wCopy, srcPtr+=pixelSize) {
+ *destPtr++ = srcPtr[0];
+ *destPtr++ = srcPtr[greenOffset];
+ *destPtr++ = srcPtr[blueOffset];
+ *destPtr++ = srcPtr[alphaOffset];
+ }
+ continue;
+ }
+
+ /*
+ * Bother; need to consider the alpha value of each pixel to
+ * know what to do.
+ */
+
+ for (; wCopy>0 ; --wCopy, srcPtr+=pixelSize) {
+ int alpha = srcPtr[alphaOffset];
+
+ if (alpha == 255 || !destPtr[3]) {
/*
- * Either this is the SET rule (we overwrite whatever
- * is there) or the destination is entirely blank. In
- * both cases, we just set the destination to the
- * source.
+ * Either the source is 100% opaque, or the
+ * destination is entirely blank. In all cases, we
+ * just set the destination to the source.
*/
*destPtr++ = srcPtr[0];
@@ -4491,12 +4515,20 @@ Tk_PhotoPutBlock(
continue;
}
+ /*
+ * Can still skip doing work if the source is 100%
+ * transparent at this point.
+ */
+
if (alpha) {
int Alpha = destPtr[3];
/*
- * This implements the Porter-Duff Source-Over
- * compositing rule.
+ * OK, there's real work to be done. Luckily, there's
+ * a substantial literature on what to do in this
+ * case. In particular, Porter and Duff have done a
+ * taxonomy of compositing rules, and the right one is
+ * the "Source Over" rule. This code implements that.
*/
destPtr[0] = PD_SRC_OVER(srcPtr[0], alpha, destPtr[0],
@@ -4508,10 +4540,6 @@ Tk_PhotoPutBlock(
destPtr[3] = PD_SRC_OVER_ALPHA(alpha, Alpha);
}
- /*
- * else should be empty space
- */
-
destPtr += 4;
}
}