Fix [fca13549b6]: TkMacOSXRGBPixel() used incorrectly in ImageGetPixel()

3 files changed, 23 insertions, 14 deletions

diff --git a/macosx/tkMacOSXColor.c b/macosx/tkMacOSXColor.c
index b4347b8..ce91520 100644
--- a/macosx/tkMacOSXColor.c
+++ b/macosx/tkMacOSXColor.c
@@ -112,11 +112,10 @@ void initColorTable()
  *	Return an unsigned long value suitable for use in the pixel
  *	field of an XColor with the specified red, green and blue
  *	intensities.  The inputs are cast as unsigned longs but are
- *      expected to have values representable by an unsigned short
- *      as used in the XColor struct.  These values are divided by
- *      256 to generate a 24-bit RGB pixel value.
+ *      expected to have values representable by an unsigned char.
  *
- *      This is called by the TkpGetPixel macro, used in xcolor.c.
+ *      This is called in the TkpGetPixel macro, used in xcolor.c,
+ *      and in ImageGetPixel.
  *
  * Results:
  *	An unsigned long that can be used as the pixel field of an XColor.
@@ -134,9 +133,9 @@ TkMacOSXRGBPixel(
 {
     MacPixel p;
     p.pixel.colortype = rgbColor;
-    p.pixel.value = (((red >> 8) & 0xff) << 16)  |
-	            (((green >> 8) & 0xff) << 8) |
-	            ((blue >> 8) & 0xff);
+    p.pixel.value = ((red & 0xff) << 16)  |
+	            ((green & 0xff) << 8) |
+	            (blue & 0xff);
     return p.ulong;
 }
 
diff --git a/macosx/tkMacOSXImage.c b/macosx/tkMacOSXImage.c
index 4691e41..0e33b23 100644
--- a/macosx/tkMacOSXImage.c
+++ b/macosx/tkMacOSXImage.c
@@ -300,7 +300,11 @@ DestroyImage(
  *	Get a single pixel from an image.
  *
  * Results:
- *	Returns the 32 bit pixel value.
+ *      The XColor structure contains an unsigned long field named pixel which
+ *      identifies the color.  This function returns the unsigned long that
+ *      would be used as the pixel value of an XColor that has the same red
+ *      green and blue components as the XImage pixel at the specified
+ *      location.
  *
  * Side effects:
  *	None.
@@ -316,13 +320,18 @@ ImageGetPixel(
 {
     unsigned char r = 0, g = 0, b = 0;
 
+    /*
+     * Compute 8 bit red green and blue values, which are passed as inputs to
+     * TkMacOSXRGBPixel to produce the pixel value.
+     */
+
     if (image && image->data) {
 	unsigned char *srcPtr = ((unsigned char*) image->data)
 		+ (y * image->bytes_per_line)
 		+ (((image->xoffset + x) * image->bits_per_pixel) / NBBY);
 
 	switch (image->bits_per_pixel) {
-	case 32:
+	case 32: /* 8 bits per channel */
 	    r = (*((unsigned int*) srcPtr) >> 16) & 0xff;
 	    g = (*((unsigned int*) srcPtr) >>  8) & 0xff;
 	    b = (*((unsigned int*) srcPtr)      ) & 0xff;
@@ -332,12 +341,12 @@ ImageGetPixel(
 		r = srcPtr[1]; g = srcPtr[2]; b = srcPtr[3];
 	    }*/
 	    break;
-	case 16:
+	case 16: /* 5 bits per channel */
 	    r = (*((unsigned short*) srcPtr) >> 7) & 0xf8;
 	    g = (*((unsigned short*) srcPtr) >> 2) & 0xf8;
 	    b = (*((unsigned short*) srcPtr) << 3) & 0xf8;
 	    break;
-	case 8:
+	case 8: /* 2 bits per channel */
 	    r = (*srcPtr << 2) & 0xc0;
 	    g = (*srcPtr << 4) & 0xc0;
 	    b = (*srcPtr << 6) & 0xc0;
@@ -345,7 +354,7 @@ ImageGetPixel(
 	    g |= g >> 2 | g >> 4 | g >> 6;
 	    b |= b >> 2 | b >> 4 | b >> 6;
 	    break;
-	case 4: {
+	case 4: { /* 1 bit per channel */
 	    unsigned char c = (x % 2) ? *srcPtr : (*srcPtr >> 4);
 
 	    r = (c & 0x04) ? 0xff : 0;
@@ -353,11 +362,12 @@ ImageGetPixel(
 	    b = (c & 0x01) ? 0xff : 0;
 	    break;
 	}
-	case 1:
+	case 1: /* Black-white bitmap. */
 	    r = g = b = ((*srcPtr) & (0x80 >> (x % 8))) ? 0xff : 0;
 	    break;
 	}
     }
+
     return TkMacOSXRGBPixel(r, g, b);
 }
 
diff --git a/macosx/tkMacOSXPort.h b/macosx/tkMacOSXPort.h
index f5c3689..4347766 100644
--- a/macosx/tkMacOSXPort.h
+++ b/macosx/tkMacOSXPort.h
@@ -168,6 +168,6 @@
 
 MODULE_SCOPE unsigned long TkMacOSXRGBPixel(unsigned long red, unsigned long green,
 					    unsigned long blue);
-#define TkpGetPixel(p) (TkMacOSXRGBPixel(p->red, p->green, p->blue))
+#define TkpGetPixel(p) (TkMacOSXRGBPixel(p->red >> 8, p->green >> 8, p->blue >> 8))
 
 #endif /* _TKMACPORT */