fb: correct invert_area image calculation
Fix the wrong calculation for inverting implemented by
commit 70685875059f
("fb: cfb: support inverting with coordinates that do not align
with the tile")
Fixed not enough consideration when the drawing area height
is eight lines or less.
Simplify to XOR calculation.
Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@gmail.com>
diff --git a/subsys/fb/cfb.c b/subsys/fb/cfb.c
index 4730d63..52b4068 100644
--- a/subsys/fb/cfb.c
+++ b/subsys/fb/cfb.c
@@ -355,27 +355,34 @@
uint8_t m = BIT_MASK((j % 8));
uint8_t b = fb->buf[index];
- if (need_reverse) {
- m = byte_reverse(m);
- b = byte_reverse(b);
+ /*
+ * Generate mask for remaining lines in case of
+ * drawing within 8 lines from the start line
+ */
+ if (remains < 8) {
+ m |= BIT_MASK((8 - (j % 8) + remains))
+ << ((j % 8) + remains);
}
- fb->buf[index] = ~(b | m) | (b & m);
+ if (need_reverse) {
+ m = byte_reverse(m);
+ }
+
+ fb->buf[index] = (b ^ (~m));
j += 7 - (j % 8);
} else if (remains >= 8) {
/* No mask required if no start or end line is included */
fb->buf[index] = ~fb->buf[index];
j += 7;
} else {
- uint8_t m = BIT_MASK(remains % 8) << (8 - (remains % 8));
+ uint8_t m = BIT_MASK(8 - remains) << (remains);
uint8_t b = fb->buf[index];
if (need_reverse) {
m = byte_reverse(m);
- b = byte_reverse(b);
}
- fb->buf[index] = ~(b | m) | (b & m);
+ fb->buf[index] = (b ^ (~m));
j += (remains - 1);
}
}
