test image

[adammaj1]

Hi

I try to add test image by Peter Kovesi

/* Apply color map to test image. See http://peterkovesi.com/projects/colourmaps/colourmaptestimage.html */

std::string ToPPM_Test(int n, const unsigned char* srgb_colormap)
{

	static const float twopi = 2.0 * M_PI;
	int jMax = 128; // height
	int iMax = 512; // width
	int colormap_size = jMax * iMax;
	
	std::string s = "P3\n"; // magic number for plain (ASCII txt) PPM
	s += std::to_string(n) + "  " + std::to_string(jMax) + "\n"; // save n=width and jMax=height to s string
	s += "255\n"; // max val
	for (int j = 0; j < jMax; j++){ // y , jMax = height
		float v = 1.0f - (j / (jMax - 1.0f));
		for (int i = 0; i < iMax; i++) // x , so here n = width. outside n = number of colors in the map
    	
		{ 
		float u = i / (iMax - 1.0f);
		// Test image formula
		float ramp = u;
		float modulation = 0.05f * std::sin(iMax / 8 * twopi * u);
		float value = ramp + v * v * modulation;
		// Applying colormap
		int k = std::round(value * (colormap_size / 3 - 1));
		if (k < 0)
			{k = 0;}
			else if (k >= colormap_size / 3) k = colormap_size / 3 - 1;
		
		
		// add RGB string to s string
		s +=  std::to_string(srgb_colormap[3 * k + 0]) + ' '
		+     std::to_string(srgb_colormap[3 * k + 1]) + ' '
		+     std::to_string(srgb_colormap[3 * k + 2]) + '\n';
		}}
    return s;
}

It gives Segmentation fault

What should I change ?

[marlam]

I don't have time to debug this, but it seems you have 0 <= k < jMax*iMax and then use k as an index to srgb_colormap, where it should be 0 <= k < n.