42 lines
1.3 KiB
JavaScript
42 lines
1.3 KiB
JavaScript
function Spectrum(id) {
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this.el = document.getElementById(id);
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this.ctx = this.el.getContext("2d");
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}
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Spectrum.prototype.draw = function(data) {
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var vis_freq = get_visible_freq_range();
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var vis_center = vis_freq.center;
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var vis_start = 0.5 - (center_freq - vis_freq.start) / bandwidth;
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var vis_end = 0.5 - (center_freq - vis_freq.end) / bandwidth;
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var data_start = Math.round(fft_size * vis_start);
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var data_end = Math.round(fft_size * vis_end);
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var data_width = data_end - data_start;
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var data_height = Math.abs(waterfall_min_level - waterfall_max_level);
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var spec_width = window.screen.width;
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var spec_height = 100;
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ctx.clearRect(0, 0, spec_width,spec_height);
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if(spec_width > data_width)
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{
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var x_ratio = data_width / spec_width;
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var y_ratio = spec_height / data_height;
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for(var x=0; x<spec_width; x++)
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{
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var y = data[data_start + j * x_ratio] * y_ratio;
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ctx.drawRect(x, 0, x+1, y);
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}
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}
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else
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{
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var x_ratio = spec_width / data_width;
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var y_ratio = spec_height / data_height;
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for(var x=0; x<data_width; x++)
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{
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var y = data[data_start + j] * y_ratio;
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ctx.drawRect(x * x_ratio, 0, (x+1) * x_ratio, y);
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}
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}
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};
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