VuoImageConvolve.c

Go to the documentation of this file.

 
#include "VuoImageRenderer.h"
#include "VuoImageConvolve.h"
#include <OpenGL/CGLMacro.h>
 
#ifdef VUO_COMPILER
VuoModuleMetadata({
                     "title" : "VuoImageConvolve",
                     "dependencies" : [
                         "VuoImageRenderer",
                         "VuoInteger",
                         "VuoReal",
                     ]
                 });
#endif
 
typedef struct
{
    VuoShader shader;
} VuoImageConvolve_internal;
 
void VuoImageConvolve_free(void *convolve)
{
    VuoImageConvolve_internal *bi = (VuoImageConvolve_internal *)convolve;
    VuoRelease(bi->shader);
    free(bi);
}
 
double VuoImageConvolve_laplacianOfGaussian(double x, double y, double radius)
{
    const double sigma = radius * .6 * sqrt(2);
    double r2 = x*x + y*y;
    // Clamp normalization term to minimum of 1, to keep the DC offset low for small sigma values.
    return -10. / sqrt(2. * M_PI * fmax(1, sigma * sigma * sigma * sigma))
         * (1. - r2/(2*sigma*sigma))
         * exp(-r2/(2*sigma*sigma));
}
 
unsigned int VuoImageConvolve_laplacianOfGaussianWidth(double radius)
{
    // Kernel width estimation from
    // "On the discrete representation of the Laplacian of Gaussian" by Steve R. Gunn
    // (Pattern Recognition 32 (1999), page 1463 - 1472).
    // µₛ where epsilon < 10^-6.
    const double mu_s = 5;
 
    // Scale as in VuoImageBlur_calculateWeights().
    const double sigma = radius * .6 * sqrt(2);
 
    return 1 + 2 * ceil(mu_s * sigma);
}
 
VuoImage VuoImageConvolve_generateMatrix(VuoImageConvolveFunction f, unsigned int width, bool removeDCOffset, double param)
{
    // Width must be odd.
    int pixelsWide = width | 1;
//  printf("pixelsWide = %d\n", pixelsWide);
 
    float *pixelFloats = (float *)malloc(sizeof(float) * pixelsWide * pixelsWide);
    double sum = 0;
    for (int y = 0; y < pixelsWide; ++y)
        for (int x = 0; x < pixelsWide; ++x)
        {
            float v = f(x - pixelsWide/2, y - pixelsWide/2, param);
            pixelFloats[y * pixelsWide + x] = v;
            sum += v;
        }
 
    if (removeDCOffset)
    {
        double offset = sum / (pixelsWide * pixelsWide);
        for (int y = 0; y < pixelsWide; ++y)
            for (int x = 0; x < pixelsWide; ++x)
                pixelFloats[y * pixelsWide + x] -= offset;
    }
 
//  double sum2 = 0;
//  for (int y = 0; y < pixelsWide; ++y)
//  {
//      for (int x = 0; x < pixelsWide; ++x)
//      {
//          sum2 += pixelFloats[y * pixelsWide + x];
//          printf("%9.5f ", pixelFloats[y * pixelsWide + x]);
//      }
//      printf("\n");
//  }
//  if (removeDCOffset)
//      printf("sum before removing DC offset = %g    after = %g\n", sum, sum2);
//  else
//      printf("sum = %g\n", sum);
 
    return VuoImage_makeFromBuffer(pixelFloats, GL_LUMINANCE, pixelsWide, pixelsWide, VuoImageColorDepth_32, ^(void *buffer){ free(pixelFloats); });
}
 
VuoImageConvolve VuoImageConvolve_make(void)
{
    VuoImageConvolve_internal *bi = (VuoImageConvolve_internal *)malloc(sizeof(VuoImageConvolve_internal));
    VuoRegister(bi, VuoImageConvolve_free);
 
    static const char *fragmentShader = VUOSHADER_GLSL_SOURCE(120,
        \n#include "VuoGlslAlpha.glsl"
        \n#include "VuoGlslBrightness.glsl"
 
        varying vec2 fragmentTextureCoordinate;
 
        uniform sampler2D image;
        uniform vec2 viewportSize;
        uniform sampler2D convolutionMatrix;
        uniform int convolutionMatrixWidth;
        uniform int channels;
        uniform float intensity;
        uniform float threshold;
        uniform int range;
 
        float weight(int x, int y)
        {
            return texture2D(convolutionMatrix, vec2(x + .5, y + .5) / float(convolutionMatrixWidth)).r;
        }
 
        void main(void)
        {
            vec2 uv = fragmentTextureCoordinate;
 
            vec4 colorSum = vec4(0.);
 
            for (int y = 0; y < convolutionMatrixWidth; y++)
                for (int x = 0; x < convolutionMatrixWidth; x++)
                {
                    float w = weight(x,y);
                    vec4 color = VuoGlsl_sample(image, uv + vec2(
                        (x - convolutionMatrixWidth/2)/viewportSize.x,
                        (y - convolutionMatrixWidth/2)/viewportSize.y
                        ));
                    color = VuoGlsl_gray(color, channels) * w;
                    colorSum += color;
                }
 
            float brightness = VuoGlsl_brightness(colorSum, 0);
            if (abs(brightness) < threshold)
                colorSum.rgb = vec3(0.);
 
            colorSum.rgb *= intensity;
 
            vec4 color = VuoGlsl_sample(image, uv);
 
            if (range == 0)      // VuoDiode_Unipolar
                colorSum.rgb = clamp(colorSum.rgb / 2. + .5, 0, color.a);
            else if (range == 1) // VuoDiode_Bipolar
                colorSum.rgb = clamp(colorSum.rgb, 0, color.a);
            else if (range == 2) // VuoDiode_Absolute
                colorSum.rgb = clamp(abs(colorSum.rgb), 0, color.a);
 
            gl_FragColor = vec4(colorSum.rgb, color.a);
        }
    );
 
    bi->shader = VuoShader_make("General Convolution Shader");
    VuoShader_addSource(bi->shader, VuoMesh_IndividualTriangles, NULL, NULL, fragmentShader);
    VuoRetain(bi->shader);
 
    return (VuoImageConvolve)bi;
}
 
VuoImage VuoImageConvolve_convolve(VuoImageConvolve convolve, VuoImage image, VuoImage convolutionMatrix, VuoThresholdType channels, double intensity, double threshold, VuoDiode range)
{
    if (!VuoImage_isPopulated(image))
        return NULL;
 
    if (!VuoImage_isPopulated(convolutionMatrix)
     || convolutionMatrix->pixelsWide != convolutionMatrix->pixelsHigh
     || !(convolutionMatrix->pixelsWide & 1)
     || !(convolutionMatrix->pixelsHigh & 1))
        return NULL;
 
    VuoImageConvolve_internal *bi = (VuoImageConvolve_internal *)convolve;
 
    VuoShader_setUniform_VuoImage  (bi->shader, "image",                  image);
    VuoShader_setUniform_VuoImage  (bi->shader, "convolutionMatrix",      convolutionMatrix);
    VuoShader_setUniform_VuoInteger(bi->shader, "convolutionMatrixWidth", convolutionMatrix->pixelsWide);
    VuoShader_setUniform_VuoInteger(bi->shader, "channels",               channels);
    VuoShader_setUniform_VuoReal   (bi->shader, "intensity",              intensity);
    VuoShader_setUniform_VuoReal   (bi->shader, "threshold",              threshold);
    VuoShader_setUniform_VuoInteger(bi->shader, "range",                  range);
 
    VuoImage convolvedImage = VuoImageRenderer_render(bi->shader, image->pixelsWide, image->pixelsHigh, VuoImage_getColorDepth(image));
    VuoImage_setWrapMode(convolvedImage, VuoImage_getWrapMode(image));
    return convolvedImage;
}