/*
 * speedy-vision.js
 * GPU-accelerated Computer Vision for JavaScript
 * Copyright 2020-2022 Alexandre Martins <alemartf(at)gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * convolution1d.glsl
 * Separable image convolution
 */

#if !defined(KERNEL_SIZE) || !defined(AXIS) || (AXIS != 0 && AXIS != 1)
#error Undefined KERNEL_SIZE / AXIS
#endif

uniform sampler2D image;
uniform float kernel[@KERNEL_SIZE@];

const ivec2 axis = ivec2(1-AXIS, AXIS);

// Shrink the code
#define S(x,k) result += pixelAtShortOffset(image, ivec2((x),(x)) * axis) * kernel[k]

void main()
{
    vec4 result = vec4(0.0f);

    #if KERNEL_SIZE == 3

    S(-1, 2);
    S( 0, 1);
    S( 1, 0);

    #elif KERNEL_SIZE == 5

    S(-2, 4);
    S(-1, 3);
    S( 0, 2);
    S( 1, 1);
    S( 2, 0);

    #elif KERNEL_SIZE == 7

    S(-3, 6);
    S(-2, 5);
    S(-1, 4);
    S( 0, 3);
    S( 1, 2);
    S( 2, 1);
    S( 3, 0);

    #elif KERNEL_SIZE == 9

    S(-4, 8);
    S(-3, 7);
    S(-2, 6);
    S(-1, 5);
    S( 0, 4);
    S( 1, 3);
    S( 2, 2);
    S( 3, 1);
    S( 4, 0);

    #elif KERNEL_SIZE == 11

    S(-5, 10);
    S(-4, 9);
    S(-3, 8);
    S(-2, 7);
    S(-1, 6);
    S( 0, 5);
    S( 1, 4);
    S( 2, 3);
    S( 3, 2);
    S( 4, 1);
    S( 5, 0);

    #elif KERNEL_SIZE == 13

    S(-6, 12);
    S(-5, 11);
    S(-4, 10);
    S(-3, 9);
    S(-2, 8);
    S(-1, 7);
    S( 0, 6);
    S( 1, 5);
    S( 2, 4);
    S( 3, 3);
    S( 4, 2);
    S( 5, 1);
    S( 6, 0);

    #elif KERNEL_SIZE == 15

    S(-7, 14);
    S(-6, 13);
    S(-5, 12);
    S(-4, 11);
    S(-3, 10);
    S(-2, 9);
    S(-1, 8);
    S( 0, 7);
    S( 1, 6);
    S( 2, 5);
    S( 3, 4);
    S( 4, 3);
    S( 5, 2);
    S( 6, 1);
    S( 7, 0);

    #else
    #error Invalid parameters
    #endif

    color = vec4(result.rgb, 1.0f);
}