Work on #209, tweak audio spectrum scaling
Originally committed to SVN as r554.
This commit is contained in:
Niels Martin Hansen
parent
5c80e6fad2
commit
c69f347035
1 changed files with 44 additions and 168 deletions
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@ -505,7 +505,7 @@ public:
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float *base_in; // audio sample data (shared)
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int samples; // number of samples per column
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int depth; // display bit depth
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float scale; // vertical scale of display
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float scale; // vertical scale of display, exponential, min=0, mid=1, max=8
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protected:
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wxThread::ExitCode Entry() {
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@ -540,23 +540,33 @@ protected:
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write_ptr = data+i+h*w;
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write_ptr16 = ((unsigned short*)data)+(i+h*w);
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// According to the formula at http://en.wikipedia.org/wiki/Fast_Fourier_transform:
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// X_k = SUM ( n=0, N-1, x_n * e^(-2*pi*i / N * n * k) )
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// The maximum output value for our case (real-valued-only input, range -16384 to +16383, N=1024)
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// must be:
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// O(X_k) = O( SUM ( n=0, 1023, 16383 * exp(-2*pi*i / 1024 * 1023 * 1023) ) )
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// = 1024 * 16383 * exp(-pi*i / 512 * 1023 * 1023)
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// ~= 16777216 * exp(-2*pi * i * 1024)
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// Since exp(ix) = cos(x) + i * sin(x), |a * exp(i*b)| = a for all real a and b, max
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// power will be 16777216.
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// More generally, in this context, it will be:
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// samples * 2^(audio_bit_depth-1)
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// Currently 16 bit audio is assumed, meaning samples*16384
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// But scale this by a user amount (vertical zoom0 -- scale is from 0 to 8
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int maxpower = window*16384 / (16*256*scale);
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// The maximum power output from the FFT
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// Derived by maximising the result from the DFT function:
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// f[u] = sum(x=0,N-1)[ f(x) * exp(-2 * pi * i * u * x) ]
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// Where N is the number of samples transformed.
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// = N * 2^(B-1) * exp(-2 * pi * i * u * x)
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// Maximising by f(x) constant at maximum sample value.
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// B is bit-depth of the samples, so 2^(B-1) is the maximum sample value.
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// = N * 2^(B-1) * [ cos(-2*pi*u*x) + i sin(-2*pi*u*x) ]
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// Expanding using Euler's formula.
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// = N * 2^(B-1) * [ cos(2*pi*u*x) - i sin(2*pi*u*x) ]
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// cos(-x) = cos(x) and sin(-x) = -sin(x)
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// = N * 2^(B-1) * cos(2*pi*u*x) - N * 2^(B-1) * i sin(2*pi*u*x) [A]
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// Expand the bracket.
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// Now determine the maximum magnitude of [A], letting u be constant and x variable.
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// | N * 2^(B-1) * cos(2*pi*u*x) - N * 2^(B-1) * i sin(2*pi*u*x) |
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// = sqrt( [N * 2^(B-1) * cos(2*pi*u*x)]^2 + [N * 2^(B-1) * sin(2*pi*u*x)]^2 )
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// = sqrt( N^2 * 4^(B-1) * cos^2(2*pi*u*x) + N^2 * 4^(B-1) * sin^2(2*pi*u*x) )
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// = sqrt( N^2 * 4^(B-1) * [ cos^2(2*pi*u*x) + sin^2(2*pi*u*x) ] )
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// = sqrt( N^2 * 4^(B-1) )
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// It's known that sin^2(x) + cos^2(x) = 1.
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// = N * 2^(B-1)
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int maxpower = (1 << (16 - 1))*256;
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// Calculate the signal power over frequency
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#ifdef SPECTRUM_LOGAGITHMIC
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#if 0
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// Logarithmic scale
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for (int j = 0; j < window; j++) {
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float t = out_r[j]*out_r[j] + out_i[j]*out_i[j];
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if (t < 1)
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@ -565,7 +575,21 @@ protected:
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power[j] = 10. * log10(t) * 64; // try changing the constant 64 if playing with this
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}
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maxpower = 10 * log10((float)maxpower);
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#elif 1
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// "Compressed" scale
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double onethirdmaxpower = maxpower / 3, twothirdmaxpower = maxpower * 2/3;
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double overscale = maxpower*8*scale - twothirdmaxpower;
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for (int j = 0; j < window; j++) {
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// First do a simple linear scale power calculation -- 8 gives a reasonable default scaling
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power[j] = sqrt(out_r[j]*out_r[j] + out_i[j]*out_i[j]) * 8 * scale;
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if (power[j] > maxpower * 2/3) {
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double p = power[j] - twothirdmaxpower;
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p = log(p) * onethirdmaxpower / log(overscale);
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power[j] = p + twothirdmaxpower;
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}
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}
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#else
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// Linear scale
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for (int j = 0; j < window; j++) {
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power[j] = sqrt(out_r[j]*out_r[j] + out_i[j]*out_i[j]);
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}
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@ -596,7 +620,7 @@ protected:
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for (int samp = sample1; samp <= sample2; samp++) {
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if (power[samp] > maxval) maxval = power[samp];
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}
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int intensity = int(maxval / maxpower);
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int intensity = int(256 * maxval / maxpower);
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WRITE_PIXEL
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}
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}
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@ -611,52 +635,12 @@ protected:
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float sample1 = power[(int)floor(ideal)+cutoff];
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float sample2 = power[(int)ceil(ideal)+cutoff];
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float frac = ideal - floor(ideal);
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int intensity = int(((1-frac)*sample1 + frac*sample2) / maxpower);
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int intensity = int(((1-frac)*sample1 + frac*sample2) / maxpower * 256);
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WRITE_PIXEL
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}
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}
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#undef WRITE_PIXEL
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// Draw bar
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/*float accum = 0;
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int accumPos = posThres;
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int y = h;
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int intensity;
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float t1,t2;
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for (int j=cutoff;j<halfwindow;j++) {
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// Calculate magnitude and add to accumulator
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t1 = out_r[j];
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t1 *= t1;
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t2 = out_i[j];
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t2 *= t2;
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t2 += t1;
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accum += sqrt(t2);
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// When accumulator goes over, plot point
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accumPos--;
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if (accumPos == 0) {
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intensity = int(accum*mult);
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if (intensity > 255) intensity = 255;
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if (intensity < 0) intensity = 0;
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// Write and go to next row
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if (depth == 32) {
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write_ptr -= w;
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*write_ptr = spectrumColorMap[intensity];
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}
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else if (depth == 16) {
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write_ptr16 -= w;
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*write_ptr16 = spectrumColorMap16[intensity];
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}
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y--;
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if (y == 0) break;
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accumPos = posThres;
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accum = 0;
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}
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}*/
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}
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delete out_r;
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@ -715,7 +699,7 @@ void AudioDisplay::DrawSpectrum(wxDC &finaldc,bool weak) {
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const int cpu_count = MAX(wxThread::GetCPUCount(), 1);
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std::vector<SpectrumRendererThread*> threads(cpu_count);
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for (int i = 0; i < cpu_count; i++) {
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// Ugh, way too many data to copy in
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// Ugh, way too much data to copy in
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threads[i] = new SpectrumRendererThread();
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threads[i]->data = data;
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threads[i]->window = window;
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@ -736,118 +720,10 @@ void AudioDisplay::DrawSpectrum(wxDC &finaldc,bool weak) {
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delete threads[i];
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}
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// Additional constants
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const int halfwindow = window/2;
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const int posThres = MAX(1,int(double(halfwindow-cutOff)/double(h)*0.5/scale + 0.5));
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const float mult = float(h)/float(halfwindow-cutOff)/255.f;
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// And more
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int *write_ptr = data;
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unsigned short *write_ptr16 = (unsigned short *)data;
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/*// More arrays
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float *out_r = new float[window];
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float *out_i = new float[window];
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int *write_ptr = data;
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unsigned short *write_ptr16 = (unsigned short *)data;
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// Prepare variables
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int halfwindow = window/2;
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int posThres = MAX(1,int(double(halfwindow-cutOff)/double(h)*0.5/scale + 0.5));
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float mult = float(h)/float(halfwindow-cutOff)/255.f;
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// Calculation loop
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for (int i=0;i<w;i++) {
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// Calculate start for current bar
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__int64 curStart = i*samples-(window/2);
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if (curStart < 0) curStart = 0;
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// Position input
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in = raw_float + curStart;
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// Perform the FFT
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FFT fft;
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fft.Transform(window,in,out_r,out_i);
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// Draw bar
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float accum = 0;
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int accumPos = posThres;
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int y = h;
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int intensity;
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float t1,t2;
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// Position pointer
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write_ptr = data+i+h*w;
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write_ptr16 = ((unsigned short*)data)+(i+h*w);
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// Draw loop
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for (int j=cutOff;j<halfwindow;j++) {
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// Calculate magnitude and add to accumulator
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t1 = out_r[j];
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t1 *= t1;
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t2 = out_i[j];
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t2 *= t2;
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t2 += t1;
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accum += sqrt(t2);
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// When accumulator goes over, plot point
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accumPos--;
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if (accumPos == 0) {
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intensity = int(accum*mult);
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if (intensity > 255) intensity = 255;
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if (intensity < 0) intensity = 0;
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// Write and go to next row
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if (depth == 32) {
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write_ptr -= w;
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*write_ptr = spectrumColorMap[intensity];
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}
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else if (depth == 16) {
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write_ptr16 -= w;
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*write_ptr16 = spectrumColorMap16[intensity];
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}
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//dc.SetPen(pen[intensity]);
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//dc.DrawPoint(i,y);
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y--;
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if (y == 0) break;
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accumPos = posThres;
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accum = 0;
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}
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}
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}*/
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////// END OF PARALLELISED CODE //////
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// Clear top of image
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/*
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// not needed with new algo, it always fill the entire image
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int filly = h - (halfwindow-cutOff)/posThres;
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if (filly < 0) filly = 0;
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if (depth == 32) {
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int color = spectrumColorMap[0];
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for (int y=0;y<filly;y++) {
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write_ptr = data+y*w;
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for (int x=0;x<w;x++) {
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*write_ptr = color;
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write_ptr++;
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}
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}
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}
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else {
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unsigned short color = spectrumColorMap16[0];
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for (int y=0;y<filly;y++) {
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write_ptr16 = ((unsigned short*)data)+y*w;
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for (int x=0;x<w;x++) {
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*write_ptr16 = color;
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write_ptr16++;
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}
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}
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}
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*/
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// Clear memory
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delete raw_float;
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// Create image
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// Create image FIXME *BREAKS ON NON-WIN32* (see wx docs)
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spectrumDisplay = new wxBitmap((const char*)data,w,h,depth);
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}
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