How to crop a part of screen to apply a shader?

[MarioMey]

[SOLVED IN NEXT COMMENT]

I would like to modify my blur.glsl shader to use as "logo blurrer". So, I would like to take a part of the screen (with uniforms values), apply blur effect and blend above the original image.

This:

To this:

For the moment, I have this (but it is wrong):

/* Simple Box Blur
 */

#pragma shaderfilter set amount__description Amount
#pragma shaderfilter set amount__default 2
#pragma shaderfilter set amount__min 0
#pragma shaderfilter set amount__max 8
#pragma shaderfilter set amount__slider true

#pragma shaderfilter set multiplier__description Multiplier
#pragma shaderfilter set multiplier__default 5.0
#pragma shaderfilter set multiplier__min 1.0
#pragma shaderfilter set multiplier__max 20.0
#pragma shaderfilter set multiplier__slider true

#pragma shaderfilter set left__description Left
#pragma shaderfilter set left__default 0.0
#pragma shaderfilter set left__min 0.0
#pragma shaderfilter set left__max 1.0
#pragma shaderfilter set left__slider true

#pragma shaderfilter set right__description Right
#pragma shaderfilter set right__default 1.0
#pragma shaderfilter set right__min 0.0
#pragma shaderfilter set right__max 1.0
#pragma shaderfilter set right__slider true

#pragma shaderfilter set top__description Top
#pragma shaderfilter set top__default 0.0
#pragma shaderfilter set top__min 0.0
#pragma shaderfilter set top__max 1.0
#pragma shaderfilter set top__slider true

#pragma shaderfilter set bottom__description Bottom
#pragma shaderfilter set bottom__default 1.0
#pragma shaderfilter set bottom__min 0.0
#pragma shaderfilter set bottom__max 1.0
#pragma shaderfilter set bottom__slider true

uniform int amount;
uniform float multiplier;

uniform float right;
uniform float left;
uniform float top;
uniform float bottom;

vec4 render(vec2 uv) {
	vec2 pix = vec2(1.0 / builtin_uv_size.x, 1.0 / builtin_uv_size.y) * multiplier;
	vec4 sum = vec4(0);
	
	int i, j;
	
	vec4 recorte = vec4(0);

    float r = texture(image, uv).x;
    float g = texture(image, uv).y;
    float b = texture(image, uv).z;
    float a = texture(image, uv).a;
	
	if ((uv.x > left && uv.x < right) && (uv.y > top && uv.y < bottom)) {
		vec4 recorte = vec4(r,g,b,0);
	}	
	else {
		vec4 recorte = vec4(r,g,b,a);
	}

	for(i = -amount; i <= amount; i++){
		for(j = -amount; j <= amount; j++){
			sum += texture2D(recorte, uv + vec2(float(i), float(j)) * pix);
		}
	}
	vec4 blur = sum / pow(amount * 2 + 1, 2);
	return blur; 
}

[MarioMey]

Done. Code could be better, optimized... but it's a cheap blur, so it doesn't matter.

/* Simple Box Blur - with Mask
 */

#pragma shaderfilter set amount__description Amount
#pragma shaderfilter set amount__default 2
#pragma shaderfilter set amount__min 0
#pragma shaderfilter set amount__max 8
#pragma shaderfilter set amount__slider true

#pragma shaderfilter set multiplier__description Multiplier
#pragma shaderfilter set multiplier__default 5.0
#pragma shaderfilter set multiplier__min 1.0
#pragma shaderfilter set multiplier__max 20.0
#pragma shaderfilter set multiplier__slider true

#pragma shaderfilter set left__description Left
#pragma shaderfilter set left__step 0.01
#pragma shaderfilter set left__default 0.0
#pragma shaderfilter set left__min 0.0
#pragma shaderfilter set left__max 1.0
#pragma shaderfilter set left__slider true

#pragma shaderfilter set right__description Right
#pragma shaderfilter set right__step 0.01
#pragma shaderfilter set right__default 1.0
#pragma shaderfilter set right__min 0.0
#pragma shaderfilter set right__max 1.0
#pragma shaderfilter set right__slider true

#pragma shaderfilter set top__description Top
#pragma shaderfilter set top__step 0.01
#pragma shaderfilter set top__default 0.0
#pragma shaderfilter set top__min 0.0
#pragma shaderfilter set top__max 1.0
#pragma shaderfilter set top__slider true

#pragma shaderfilter set bottom__description Bottom
#pragma shaderfilter set bottom__step 0.01
#pragma shaderfilter set bottom__default 1.0
#pragma shaderfilter set bottom__min 0.0
#pragma shaderfilter set bottom__max 1.0
#pragma shaderfilter set bottom__slider true

uniform int amount;
uniform float multiplier;

uniform float left;
uniform float right;
uniform float top;
uniform float bottom;

vec4 render(vec2 uv) {
	vec2 pix = vec2(1.0 / builtin_uv_size.x, 1.0 / builtin_uv_size.y) * multiplier;
	vec4 sum = vec4(0);
	
	vec4 orig = texture(image,uv);
	vec4 box  = vec4(0.0);
	
	int i, j;
	for(i = -amount; i <= amount; i++){
		for(j = -amount; j <= amount; j++){
			
			sum += texture(image, uv + vec2(float(i), float(j)) * pix);

			float l =  left   + float(i) * pix.x;
			float r =  right  + float(i) * pix.x;
			float t =  top    + float(j) * pix.y;
			float b =  bottom + float(j) * pix.y;
			float a = float(int(((uv.x > l && uv.x < r) && (uv.y > t && uv.y < b))));
			
			box += mix(vec4(0.0), vec4(1.0), a);
		}
	}

	vec4 blur = sum / pow(amount * 2 + 1, 2);
	vec4 mask = box / pow(amount * 2 + 1, 2);
	vec4 result = mix(orig, blur, mask);
	
	return result;
}

[Limeth]

Hello, another option would be duplicating the source and using the "Crop/Pad" filter on it prior to your own filter.

[MarioMey]

I don't think is a good option. OBS doesn't let you make a reference-copy of a video-source because it is not advisable to access the same file twice. That's why "Paste (Duplicate)" doesn't work on video sources.

You can do it by adding the file twice... but you might have problems with it.

[MarioMey]

In the process I thought there was another option. Something like using this line: sum += texture(image, uv + vec2(float(i), float(j)) * pix); but taking the already cropped image. The problem is that I can't use texture(vec4, uv): it needs a sample2D. I should find another way to change UV coordinates of a vec4. If you know, please enlighten me.