okay i figured it out

shader_type canvas_item;

const vec2 center_original = vec2(0.5, 0.5);
uniform vec2 center_actual = vec2(0.5, 0.5);

void fragment() {
    vec2 adjusted_uv = vec2(0.0, 0.0);
    if (UV.x < center_actual.x){
        adjusted_uv.x = UV.x * center_original.x / center_actual.x;
    } else {
        adjusted_uv.x = UV.x * (1.0 - center_original.x) / (1.0 - center_actual.x) + 1.0 - (1.0 - center_original.x) / (1.0 - center_actual.x);
    }
    if (UV.y < center_actual.y){
        adjusted_uv.y = UV.y * center_original.y / center_actual.y;
    } else {
        adjusted_uv.y = UV.y * (1.0 - center_original.y) / (1.0 - center_actual.y) + 1.0 - (1.0 - center_original.y) / (1.0 - center_actual.y);
    }
    COLOR = texture(TEXTURE, adjusted_uv);
}
```

okay i figured it out

shader_type canvas_item;

const vec2 center_original = vec2(0.5, 0.5);
uniform vec2 center_actual = vec2(0.5, 0.5);

void fragment() {
    vec2 adjusted_uv = vec2(0.0, 0.0);
    if (UV.x < center_actual.x){
        adjusted_uv.x = UV.x * center_original.x / center_actual.x;
    } else {
        adjusted_uv.x = UV.x * (1.0 - center_original.x) / (1.0 - center_actual.x) + 1.0 - (1.0 - center_original.x) / (1.0 - center_actual.x);
    }
    if (UV.y < center_actual.y){
        adjusted_uv.y = UV.y * center_original.y / center_actual.y;
    } else {
        adjusted_uv.y = UV.y * (1.0 - center_original.y) / (1.0 - center_actual.y) + 1.0 - (1.0 - center_original.y) / (1.0 - center_actual.y);
    }
    COLOR = texture(TEXTURE, adjusted_uv);
}