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pixel: correct and clarify code for monochrome get/set pixels

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Signed-off-by: deadprogram <ron@hybridgroup.com>
This commit is contained in:
deadprogram
2024-10-27 13:03:33 +01:00
parent b7bbecc456
commit 6301627338
1 changed files with 8 additions and 6 deletions
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pixel/image.go
+8 -6
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@@ -139,14 +139,15 @@ func (img Image[T]) setPixel(index int, c T) {
case zeroColor.BitsPerPixel() == 1: case zeroColor.BitsPerPixel() == 1:
// Monochrome. // Monochrome.
x := index % int(img.width) x := index % int(img.width)
y := index / int(img.width) offset := index / 8
offset := x + (y/8)*int(img.width)
ptr := (*byte)(unsafe.Add(img.data, offset)) ptr := (*byte)(unsafe.Add(img.data, offset))
if c != zeroColor { if c != zeroColor {
*((*byte)(ptr)) |= 1 << uint8(y%8) *((*byte)(ptr)) |= (1 << (7 - uint8(x%8)))
} else { } else {
*((*byte)(ptr)) &^= 1 << uint8(y%8) *((*byte)(ptr)) &^= (1 << (7 - uint8(x%8)))
} }
return return
case zeroColor.BitsPerPixel()%8 == 0: case zeroColor.BitsPerPixel()%8 == 0:
// Each color starts at a whole byte offset. // Each color starts at a whole byte offset.
@@ -200,9 +201,10 @@ func (img Image[T]) Get(x, y int) T {
case zeroColor.BitsPerPixel() == 1: case zeroColor.BitsPerPixel() == 1:
// Monochrome. // Monochrome.
var c Monochrome var c Monochrome
offset := x + (y/8)*int(img.width) offset := index / 8
bits := index - (offset * 8)
ptr := (*byte)(unsafe.Add(img.data, offset)) ptr := (*byte)(unsafe.Add(img.data, offset))
c = (*ptr >> uint8(y%8) & 0x1) == 1 c = ((*ptr >> (7 - uint8(bits))) & 0x1) > 0
return any(c).(T) return any(c).(T)
case zeroColor.BitsPerPixel()%8 == 0: case zeroColor.BitsPerPixel()%8 == 0:
// Colors like RGB565, RGB888, etc. // Colors like RGB565, RGB888, etc.