How to draw pixel-level color gradients in CScrollView ?

I have a very general question. I wish to plot a mathematical function on a 2-dimensional grid. The function will be represented by 3 sets of floats, x-values, y-values, and z-values. Obviously, it is impossible to plot 3 such data sets on a 2D grid, so one approach is to use pixel coloration to represent the z-values.

Those examples (and there are many to be found) show something like the function of the complex variable z, f(z) = exp(z). I have attached a exp(z).jpg example of the imaginary part of the plot exp(z).

My question is: How to accomplish such a gradient colorization, assuming one already has the data?

I have experimented with Gdiplus SetPixel, but I have not figured out how to produce a smooth gradient. Obviously, I'm in way over my head, but I had hoped someone might lead me in the right direction.

Here's my attempt to create a simple gradient:

Code:

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        CDC * pDC = GetDC();
        Graphics graphics(pDC->m_hDC);

        CRect r;
        GetWindowRect(&r);
        ScreenToClient(&r);

        HWND hwnd = GetSafeHwnd();
        CDC * pdc = GetDC();
        HDC hdc = ::GetDC(hwnd);
        COLORREF cr = RGB(192, 192, 192);
        for(int x = 10; x <= 600; x++)
        {
                for(int y = 10; y <= 400; y++)
                {
                        SetPixelV(hdc, x, y, cr);
                        cr += 1;
                }
        }

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You can see my lame result also attached mygrad.jpg. Your thoughts greatly appreciated. How would you do this ?

Quote:

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Originally Posted by Mike Pliam

My question is: How to accomplish such a gradient colorization, assuming one already has the data?

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You have to create a legend that associates certain values with certain colors and then interpolate intermediate values. Easiest way to interpolate colors is by just taking a linear combination of the red, green and blue values.

Quote:

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Originally Posted by Mike Pliam

I have experimented with Gdiplus SetPixel, but I have not figured out how to produce a smooth gradient. Obviously, I'm in way over my head, but I had hoped someone might lead me in the right direction.

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Besides the fact that you don't release the DCs, your use of SetPixelV seems ok, though that function can be slow. It's faster to assign to a bitmap of a memory DC and then bitblit to the window DC.
However, what is "cr += 1;" supposed to accomplish?

I'd suggest to forget about the graph and focus on the first problem first: how to assign a color to a value?