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gx: implement C1.over(C2), add gx.cyan and gx.magenta, fix + and - ops, add more tests

This commit is contained in:
Delyan Angelov 2022-01-29 21:40:02 +02:00
parent a4fb5d2cfd
commit afd3ca8273
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GPG Key ID: 66886C0F12D595ED
2 changed files with 134 additions and 34 deletions

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@ -1,9 +1,19 @@
module gx module gx
pub const ( pub const (
blue = Color{ black = Color{
r: 0 r: 0
g: 0 g: 0
b: 0
}
gray = Color{
r: 128
g: 128
b: 128
}
white = Color{
r: 255
g: 255
b: 255 b: 255
} }
red = Color{ red = Color{
@ -16,11 +26,26 @@ pub const (
g: 255 g: 255
b: 0 b: 0
} }
blue = Color{
r: 0
g: 0
b: 255
}
yellow = Color{ yellow = Color{
r: 255 r: 255
g: 255 g: 255
b: 0 b: 0
} }
magenta = Color{
r: 255
g: 0
b: 255
}
cyan = Color{
r: 0
g: 255
b: 255
}
orange = Color{ orange = Color{
r: 255 r: 255
g: 165 g: 165
@ -31,16 +56,6 @@ pub const (
g: 0 g: 0
b: 128 b: 128
} }
black = Color{
r: 0
g: 0
b: 0
}
gray = Color{
r: 128
g: 128
b: 128
}
indigo = Color{ indigo = Color{
r: 75 r: 75
g: 0 g: 0
@ -56,11 +71,6 @@ pub const (
g: 130 g: 130
b: 238 b: 238
} }
white = Color{
r: 255
g: 255
b: 255
}
dark_blue = Color{ dark_blue = Color{
r: 0 r: 0
g: 0 g: 0
@ -139,21 +149,55 @@ pub fn rgba(r byte, g byte, b byte, a byte) Color {
} }
} }
pub fn (c Color) + (c2 Color) Color { // + adds `b` to `a`, with a maximum value of 255 for each channel
pub fn (a Color) + (b Color) Color {
mut na := int(a.a) + b.a
mut nr := int(a.r) + b.r
mut ng := int(a.g) + b.g
mut nb := int(a.b) + b.b
if na > 255 {
na = 255
}
if nr > 255 {
nr = 255
}
if ng > 255 {
ng = 255
}
if nb > 255 {
nb = 255
}
return Color{ return Color{
r: c.r + c2.r r: byte(nr)
g: c.g + c2.g g: byte(ng)
b: c.b + c2.b b: byte(nb)
a: c.a + c2.a a: byte(na)
} }
} }
pub fn (c Color) - (c2 Color) Color { // - subtracts `b` from `a`, with a minimum value of 0 for each channel
pub fn (a Color) - (b Color) Color {
mut na := if a.a > b.a { a.a } else { b.a }
mut nr := int(a.r) - b.r
mut ng := int(a.g) - b.g
mut nb := int(a.b) - b.b
if na < 0 {
na = 0
}
if nr < 0 {
nr = 0
}
if ng < 0 {
ng = 0
}
if nb < 0 {
nb = 0
}
return Color{ return Color{
r: c.r - c2.r r: byte(nr)
g: c.g - c2.g g: byte(ng)
b: c.b - c2.b b: byte(nb)
a: c.a - c2.a a: byte(na)
} }
} }
@ -175,6 +219,24 @@ pub fn (c Color) / (c2 Color) Color {
} }
} }
// over - implements an `a` over `b` operation.
// see https://keithp.com/~keithp/porterduff/p253-porter.pdf
pub fn (a Color) over(b Color) Color {
aa := f32(a.a) / 255
ab := f32(b.a) / 255
ar := aa + ab * (1 - aa)
//
rr := (f32(a.r) * aa + f32(b.r) * ab * (1 - aa)) / ar
gr := (f32(a.g) * aa + f32(b.g) * ab * (1 - aa)) / ar
br := (f32(a.b) * aa + f32(b.b) * ab * (1 - aa)) / ar
return Color{
r: byte(rr)
g: byte(gr)
b: byte(br)
a: byte(ar * 255)
}
}
pub fn (c Color) eq(c2 Color) bool { pub fn (c Color) eq(c2 Color) bool {
return c.r == c2.r && c.g == c2.g && c.b == c2.b && c.a == c2.a return c.r == c2.r && c.g == c2.g && c.b == c2.b && c.a == c2.a
} }

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@ -4,38 +4,47 @@ fn test_hex() {
// valid colors // valid colors
a := gx.hex(0x6c5ce7ff) a := gx.hex(0x6c5ce7ff)
b := gx.rgba(108, 92, 231, 255) b := gx.rgba(108, 92, 231, 255)
assert a.eq(b) assert a == b
// doesn't give right value with short hex value // doesn't give right value with short hex value
short := gx.hex(0xfff) short := gx.hex(0xfff)
assert !short.eq(gx.white) assert short != gx.white
assert short == gx.Color{0, 0, 15, 255}
} }
fn test_add() { fn test_add() {
a := gx.rgba(100, 100, 100, 100) a := gx.rgba(100, 100, 100, 100)
b := gx.rgba(100, 100, 100, 100) b := gx.rgba(100, 100, 100, 100)
r := gx.rgba(200, 200, 200, 200) r := gx.rgba(200, 200, 200, 200)
assert (a + b).eq(r) assert (a + b) == r
//
assert gx.red + gx.green == gx.yellow
assert gx.red + gx.blue == gx.magenta
assert gx.green + gx.blue == gx.cyan
} }
fn test_sub() { fn test_sub() {
a := gx.rgba(100, 100, 100, 100) a := gx.rgba(100, 100, 100, 50)
b := gx.rgba(100, 100, 100, 100) b := gx.rgba(100, 100, 100, 100)
r := gx.rgba(0, 0, 0, 0) r := gx.rgba(0, 0, 0, 100)
assert (a - b).eq(r) assert (a - b) == r
//
assert gx.white - gx.green == gx.magenta
assert gx.white - gx.blue == gx.yellow
assert gx.white - gx.red == gx.cyan
} }
fn test_mult() { fn test_mult() {
a := gx.rgba(10, 10, 10, 10) a := gx.rgba(10, 10, 10, 10)
b := gx.rgba(10, 10, 10, 10) b := gx.rgba(10, 10, 10, 10)
r := gx.rgba(100, 100, 100, 100) r := gx.rgba(100, 100, 100, 100)
assert (a * b).eq(r) assert (a * b) == r
} }
fn test_div() { fn test_div() {
a := gx.rgba(100, 100, 100, 100) a := gx.rgba(100, 100, 100, 100)
b := gx.rgba(10, 10, 10, 10) b := gx.rgba(10, 10, 10, 10)
r := gx.rgba(10, 10, 10, 10) r := gx.rgba(10, 10, 10, 10)
assert (a / b).eq(r) assert (a / b) == r
} }
fn test_rgba8() { fn test_rgba8() {
@ -61,3 +70,32 @@ fn test_abgr8() {
assert gx.green.abgr8() == -16711936 assert gx.green.abgr8() == -16711936
assert gx.blue.abgr8() == -65536 assert gx.blue.abgr8() == -65536
} }
fn test_over() {
// shorten names:
r := gx.red
g := gx.green
b := gx.blue
y := gx.yellow
semi_r := gx.Color{255, 0, 0, 128}
semi_g := gx.Color{0, 255, 0, 128}
semi_b := gx.Color{0, 0, 255, 128}
// fully opaque colors, should be preserved when layed *over* any others:
assert b.over(g) == b
assert r.over(g) == r
assert y.over(r) == y
assert g.over(r) == g
// half transparent pure colors, *over* pure colors, should preserve them correspondingly:
assert semi_r.over(r) == gx.Color{255, 0, 0, 255} // preserve pure red
assert semi_r.over(g) == gx.Color{128, 126, 0, 255}
assert semi_r.over(b) == gx.Color{128, 0, 126, 255}
assert semi_g.over(r) == gx.Color{126, 128, 0, 255}
assert semi_g.over(g) == gx.Color{0, 255, 0, 255} // preserve pure green
assert semi_g.over(b) == gx.Color{0, 128, 126, 255}
assert semi_b.over(r) == gx.Color{126, 0, 128, 255}
assert semi_b.over(g) == gx.Color{0, 126, 128, 255}
assert semi_b.over(b) == gx.Color{0, 0, 255, 255} // preserve pure blue
}