Draw the default background color behind images. This makes images with...

Draw the default background color behind images. This makes images with alpha<1 areas look nice. It's unfortunate that the "real" background color isn't available since the image y position uses those bits, but this is a good start. Issue 5723.

sources/iTermBackgroundColorRun.m

@@ -29,10 +29,15 @@ static void iTermMakeBackgroundColorRun(iTermBackgroundColorRun *run,
     } else {
         run->isMatch = NO;
     }
-    run->bgColor = theLine[coord.x].backgroundColor;
-    run->bgGreen = theLine[coord.x].bgGreen;
-    run->bgBlue = theLine[coord.x].bgBlue;
-    run->bgColorMode = theLine[coord.x].backgroundColorMode;
+    if (theLine[coord.x].image) {
+        run->bgColor = run->bgGreen = run->bgBlue = ALTSEM_DEFAULT;
+        run->bgColorMode = ColorModeAlternate;
+    } else {
+        run->bgColor = theLine[coord.x].backgroundColor;
+        run->bgGreen = theLine[coord.x].bgGreen;
+        run->bgBlue = theLine[coord.x].bgBlue;
+        run->bgColorMode = theLine[coord.x].backgroundColorMode;
+    }
 }
 @implementation iTermBackgroundColorRunsInLine

sources/iTermTextDrawingHelper.m

@@ -2054,9 +2054,6 @@ static BOOL iTermTextDrawingHelperIsCharacterDrawable(screen_char_t *c,
     [transform scaleXBy:1.0 yBy:-1.0];
     [transform concat];
     
-    NSColor *backgroundColor = [self defaultBackgroundColor];
-    [backgroundColor set];
-    NSRectFill(NSMakeRect(0, 0, _cellSize.width * length, _cellSize.height));
     if (imageInfo.animated) {
         [_delegate drawingHelperDidFindRunOfAnimatedCellsStartingAt:origin ofLength:length];
         _animated = YES;