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[kandinsky/color] Blend identical colors

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KDColor::blend used to produce different colors when blending two
identical colors (ex : use draw_string in Python to print white text on
a white background).
blend now escapes early when its two color arguments are identical.

Change-Id: I01dc5a0d5e4e6a20e09fee0f346dafc313dae97b
This commit is contained in:
Gabriel Ozouf
2020-08-13 18:09:16 +02:00
committed by EmilieNumworks
parent d154611023
commit 38e15da5d0
1 changed files with 9 additions and 5 deletions
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14
kandinsky/src/color.cpp
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@@ -7,7 +7,11 @@ KDColor KDColor::blend(KDColor first, KDColor second, uint8_t alpha) {
* dealt with. So let's make a special case for them. */
if (alpha == 0) {
return second;
} else if (alpha == 0xFF) {
}
if (alpha == 0xFF) {
return first;
}
if (first == second) {
return first;
}
@@ -21,8 +25,8 @@ KDColor KDColor::blend(KDColor first, KDColor second, uint8_t alpha) {
uint16_t blue = first.blue()*alpha + second.blue()*oneMinusAlpha;
return RGB888(red>>8, green>>8, blue>>8);
// Blend White + black, ask for white
// white.red() = 0x1F << 3 = 0xF8
// white.red() * 0xFF = 0xF708, we wanted 0xF800
/* The formula used to blend colors produces some unwanted results :
* blend white + black, alpha = OxFF (should be white)
* white.red() * OxFF = OxF708, while we would like 0xF800
* Escaping early solves this issue. */
}