add a saturation condition to a glsl shader

[geextah_2]

Hi, I have this vibrance shader, It has an srgb threshold which can be adjusted. But the shader affects all saturation levels/%. I would like to leave colors that have a saturation under 80% unaffected, and target the above 90% saturation pixels, with a smooth transition between them (80-90%). So the first condition is the srgb threshold and the 2nd condition would be the pixel saturation. From my understanding this shader already checks saturation levels but I don't know how this works. Any help would be appreciated
side note: I don't understand shaders, I just want to make this one adjustment.

//!PARAM vibr 
//!DESC Saturates/deSaturates 
//!TYPE float 
//!MINIMUM -1 
-0.3  

//!HOOK MAIN 
//!BIND HOOKED 
//!DESC Vibrance 
 
#define CoefLuma vec4(0.2126, 0.7152, 0.0722, 0) //sRGB, HDTV 
float Thresh = 45.0/255.0; 
float w = 10.0/255.0; 
 
vec4 hook() { 
vec4 c0 = HOOKED_texOff(0); 
float lum = (c0.r + c0.g + c0.b)/3.0; 
 
float colorSat = max(max(c0.r, c0.g), c0.b) -min(min(c0.r, c0.g), c0.b); // >=0, 5 arithmetic
vec3 sat = mix(vec3(dot(c0, CoefLuma)), c0.rgb, 1+vibr -colorSat*abs(vibr)); 
float delta = smoothstep( Thresh-w, Thresh+w, lum); 
c0.rgb = mix( sat, c0.rgb, delta); 
return c0; 
}

[sophisticles]

Start with something like this and go from there:

//!PARAM vibr
//!DESC Saturates/deSaturates
//!TYPE float
//!MINIMUM -1
-0.3

//!HOOK MAIN
//!BIND HOOKED
//!DESC Vibrance

#define CoefLuma vec4(0.2126, 0.7152, 0.0722, 0) //sRGB, HDTV
float Thresh = 45.0/255.0;
float w = 10.0/255.0;

vec4 hook() {
vec4 c0 = HOOKED_texOff(0);

// Calculate saturation of the pixel's color
float colorSat = max(max(c0.r, c0.g), c0.b) - min(min(c0.r, c0.g), c0.b);

// Check if saturation is above 90%
if (colorSat > 0.9) {
// Calculate luminance
float lum = dot(c0.rgb, CoefLuma.rgb);

// Calculate smoothstep value for transition between 80-90% saturation
float smoothstepValue = smoothstep(0.8, 0.9, colorSat);

// Calculate the adjusted saturation
vec3 adjustedSaturation = mix(vec3(dot(c0.rgb, CoefLuma.rgb)), c0.rgb, 1.0 + vibr - colorSat * abs(vibr));

// Apply the effect with smooth transition
c0.rgb = mix(c0.rgb, adjustedSaturation, smoothstepValue);
}
else if (colorSat < 0.8) {
// Leave colors with saturation under 80% unaffected
return c0;
}

// Calculate luminance
float lum = (c0.r + c0.g + c0.b) / 3.0;

float delta = smoothstep(Thresh - w, Thresh + w, lum);
c0.rgb = mix(vec3(dot(c0.rgb, CoefLuma.rgb)), c0.rgb, 1.0 + vibr - colorSat * abs(vibr));
c0.rgb = mix(c0.rgb, c0.rgb, delta);

return c0;
}

[geextah_2]

Thank you for your answer. I tried this out and there is no effect visible. The shader is running but I guess something is not working properly.

[sophisticles]

Any error messages?

[geextah_2]

No, I use this in mpv, it is not capable of showing any error messages. But if there would be a code error, the shader wouldn't load at all. The shader is loaded and runs in the pipeline but there is no visible change/effect to the image.

Here are some screenshots so you have a visual representation of what we are talking about

This is how the shader worked before your tweaks, it targets the set srgb threshold "float Thresh = 45.0/255.0"

[Attachment 78736 - Click to enlarge]
This is the normal image without any shaders or when I run the shader with your tweaks

[Attachment 78737 - Click to enlarge]
Here you can see the saturation of the suit, it's at 98%, so it shuld be affected by the shader

[Attachment 78738 - Click to enlarge]

[geextah_2]

Sorry, it works. I tested it with an HDR file instead of SDR, my bad. Do you know why it isn't working on HDR? The original shader worked on both.

[sophisticles]

Sorry, I had lost this thread.

Give me a day or two to look into the HDR issue.

[geextah_2]

No problem. That would be awesome, thank you

This is an improved version, with less hard edges, better smoothstep

//!PARAM vibr
//!DESC Saturates/deSaturates
//!TYPE float
//!MINIMUM -1
-0.5

//!HOOK MAIN
//!BIND HOOKED
//!DESC Vibrance

#define CoefLuma vec4(0.2126, 0.7152, 0.0722, 0) //sRGB, HDTV
float Thresh = 200.0/255.0;
float w = 10.0/255.0;

vec4 hook() {
	vec4 c0 = HOOKED_texOff(0);
	float lum = (c0.r + c0.g + c0.b)/3.0;

	float colorSat = max(max(c0.r, c0.g), c0.b) - min(min(c0.r, c0.g), c0.b); 
	vec3 sat = mix(vec3(dot(c0, CoefLuma)), c0.rgb, 1+vibr - colorSat*abs(vibr));
	float delta = smoothstep(Thresh-w, Thresh+w, lum);
	sat = mix(sat, c0.rgb, delta);
	delta = smoothstep(0.8, 0.9, colorSat);
	c0.rgb = mix(c0.rgb, sat, delta);
	return c0;
}

Here you can see the comparison

Hard edge

[Attachment 78852 - Click to enlarge]

Smooth

[Attachment 78853 - Click to enlarge]