colors with transparency (to fix later)

src/color.zig

@@ -18,16 +18,45 @@ pub const RGB = struct {
     }
 };
 
-// pub const Default256 = [_]RGB{
-//     RGB{ .r = 0, .g = 0, .b = 0 },
-//     RGB{ .r = 204, .g = 4, .b = 3 },
-//     RGB{ .r = 25, .g = 203, .b = 0 },
-//     RGB{ .r = 206, .g = 203, .b = 0 },
-//     RGB{ .r = 13, .g = 115, .b = 204 },
-//     RGB{ .r = 203, .g = 30, .b = 209 },
-//     RGB{ .r = 13, .g = 205, .b = 205 },
-//     RGB{ .r = 221, .g = 221, .b = 221 },
-// };
+pub const RGBA = struct {
+    r: f32,
+    g: f32,
+    b: f32,
+    /// Alpha channel between 0.0 - 1.0
+    a: f32 = 1.0,
+
+    /// Create from string at comptime
+    pub fn init(comptime string: []const u8) !RGBA {
+        std.debug.assert(string.len == 8 or string.len == 9);
+        comptime var index: usize = 0;
+        if (string[0] == '#') index += 1;
+        const r = try fmt.parseInt(u8, string[index .. index + 2], 16);
+        const g = try fmt.parseInt(u8, string[index + 2 .. index + 4], 16);
+        const b = try fmt.parseInt(u8, string[index + 4 .. index + 6], 16);
+        const a = try fmt.parseInt(u8, string[index + 6 .. index + 8], 16);
+        return .{
+            .r = @as(f32, @floatFromInt(r)) / 0xff,
+            .g = @as(f32, @floatFromInt(g)) / 0xff,
+            .b = @as(f32, @floatFromInt(b)) / 0xff,
+            .a = @as(f32, @floatFromInt(a)) / 0xff,
+        };
+    }
+
+    pub fn blend(base: *const RGBA, add: *const RGBA) RGBA {
+        var r: RGBA = undefined;
+        r.a = 1 - (1 - add.a) * (1 - base.a);
+        if (r.a < std.math.floatEps(f32)) {
+            r.r = 0;
+            r.g = 0;
+            r.b = 0;
+            return r;
+        }
+        r.r = (add.r * add.a / r.a + base.r * base.a * (1 - add.a)) / r.a;
+        r.g = (add.g * add.a / r.a + base.g * base.a * (1 - add.a)) / r.a;
+        r.b = (add.b * add.a / r.a + base.b * base.a * (1 - add.a)) / r.a;
+        return r;
+    }
+};
 
 test "RGB init from string" {
     const red = try RGB.init("#ff0000");
@@ -47,3 +76,18 @@ test "RGB init from string" {
 
     try std.testing.expectError(fmt.ParseIntError.InvalidCharacter, RGB.init("xyzxyz"));
 }
+
+test "RGBA blend" {
+    const red = RGBA{ .r = 1.0, .g = 0, .b = 0, .a = 0.0 };
+    const blue = RGBA{ .r = 0, .g = 0, .b = 1.0, .a = 0.0 };
+    const result = red.blend(&blue);
+    std.debug.print("\n{any}\n", .{result});
+    const reeb = RGBA{ .r = 1.0, .g = 0, .b = 0, .a = 1.0 };
+    const blueb = RGBA{ .r = 0, .g = 0, .b = 1.0, .a = 0.0 };
+    const resultt = reeb.blend(&blueb);
+    std.debug.print("{any}\n", .{resultt});
+    const roob = RGBA{ .r = 1.0, .g = 0, .b = 0, .a = 0.5 };
+    const bloob = RGBA{ .r = 0, .g = 0, .b = 1.0, .a = 0.5 };
+    const resulttt = roob.blend(&bloob);
+    std.debug.print("{any}\n", .{resulttt});
+}