HUE control

🎨 Hue Control Shader

This shader applies a smooth hue shift to a 2D texture by converting its colors from RGB to HSV, adjusting the hue, and converting it back to RGB.
It allows full control over the hue rotation, enabling dynamic color shifting for sprites, UI elements, or special effects.

🧪 What it does:

• Converts each pixel’s color from RGB to HSV.

• Adds a hue offset (from 0.0 to 1.0) to rotate the color wheel.

• Converts the shifted color back to RGB.

• Maintains original alpha (transparency).

🎛️ Parameters:

• hue_shift float (0.0 – 1.0):
  The amount to shift the hue.
  0.0 = no change, 0.5 = 180° rotation, 1.0 = full loop back to original color.

📦 Use Cases:

• Sprite recoloring without swapping textures

• Animated color transitions

• Customizable themes or palette cycling

• Stylized effects (e.g. psychedelic glow, mood tinting)

Shader code

shader_type canvas_item;

// Base texture
uniform sampler2D tex : hint_default_black;

// Amount of hue shift (0.0 to 1.0, where 1.0 = 360° rotation)
uniform float hue_shift = 0.1;

// Converts RGB to HSV color space
vec3 rgb_to_hsv(vec3 color_rgb) {
    vec4 k = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
    vec4 p = mix(vec4(color_rgb.bg, k.wz), vec4(color_rgb.gb, k.xy), step(color_rgb.b, color_rgb.g));
    vec4 q = mix(vec4(p.xyw, color_rgb.r), vec4(color_rgb.r, p.yzx), step(p.x, color_rgb.r));

    float d = q.x - min(q.w, q.y);
    float e = 1e-10;

    return vec3(
        abs(q.z + (q.w - q.y) / (6.0 * d + e)),
        d / (q.x + e),
        q.x
    );
}

// Converts HSV back to RGB
vec3 hsv_to_rgb(vec3 color_hsv) {
    vec3 rgb = clamp(
        abs(mod(color_hsv.x * 6.0 + vec3(0.0, 4.0, 2.0), 6.0) - 3.0) - 1.0,
        0.0,
        1.0
    );
    return color_hsv.z * mix(vec3(1.0), rgb, color_hsv.y);
}

// Applies hue shifting via HSV conversion
vec4 apply_hue_shift(vec2 uv_coords, sampler2D texture_input, float shift_amount) {
    vec4 base_color = texture(texture_input, uv_coords);
    vec3 hsv = rgb_to_hsv(base_color.rgb);
    hsv.x = mod(hsv.x + shift_amount, 1.0); // wrap hue in [0,1]
    vec3 shifted_rgb = hsv_to_rgb(hsv);
    return vec4(shifted_rgb, base_color.a);
}

void fragment() {
    COLOR = apply_hue_shift(UV, tex, hue_shift);
}

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