How do I parse a shader from ShaderToy into a GLSL for Android use?

Question

First of all I'm a complete noob when it comes to shaders and GLSL. So, here is the thing:
I'm trying to parse this ShaderToy shader into a GLSL Shader Fragment to use inside this GPUImage lib. I'm using this file as a sample for the parsing.

Original

// Fork of "Simple Film Grain Shader" by terchapone. https://shadertoy.com/view/3sGGRz
// 2022-04-24 03:48:40

const float grainFactor = 0.1; //[0.0, 1.0]

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord/iResolution.xy;

    // Calculate noise and sample texture
    float mdf = grainFactor; // increase for noise amount 
    float noise = (fract(sin(dot(uv, vec2(12.9898,78.233)*2.0)) * 43758.5453));
    vec4 tex = texture(iChannel0, uv);  
    vec4 col = tex - noise * mdf;

    // Output to screen
    fragColor = col;
}

The result I got is the following

uniform sampler2D inputImageTexture;
varying highp vec2 textureCoordinate;

uniform lowp float grain;

void main(){
    lowp vec4 source = texture2D(inputImageTexture, textureCoordinate);
    
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = textureCoordinate.xy ;

    // Calculate noise and sample texture
    float mdf = grain; // increase for noise amount 
    float noise = (fract(sin(dot(uv, vec2(12.9898,78.233)*2.0)) * 43758.5453));
    
    vec4 col = source - (noise * mdf);

    // Output to screen
    gl_FragColor = col;
}

When I'm altering the grain value between 0f and 1f, the output I'm getting is diagonal dotted lines. What am I doing wrong here?

If it's completely bad, how can I get a Film Grain shader to work here? Any ideas?