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January 16, 2017 02:35
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Edge detection example explained using 1D toy example.
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| clc; clear all; close all; | |
| % Data Generation | |
| x = 0:10:2000; | |
| y = sigmf(x,[0.1 1000]); | |
| n = rand(1,201)/40 - 0.0125; | |
| f = y;% + n; | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 8 2]); | |
| plot(x,f), ylim([-0.2 1.2]), grid on; | |
| saveas(fig,'signal.png'); | |
| % Filter Generation | |
| h = fspecial('gaussian', [1 21], 2.5); | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 2 2]); | |
| plot(0:20,h), grid on | |
| saveas(gcf,'filter.png') | |
| % Derivative of filter | |
| dh = h(2:end) - h(1:end-1); | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 2 2]); | |
| plot(0:19,dh), grid on; | |
| saveas(gcf,'dfilter.png') | |
| % Second order derivative of filter | |
| d2h = dh(2:end) - dh(1:end-1); | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 2 2]); | |
| plot(0:18,d2h), grid on; | |
| saveas(gcf,'d2filter.png') | |
| % Conv data and filter | |
| hf = conv(f,h,'same'); | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 8 2]); | |
| plot(0:200,hf), ylim([-0.2 1.2]), grid on; | |
| saveas(gcf,'convdatafilter.png') | |
| % Derivative of a conv | |
| dhf1 = hf(2:end) - hf(1:end-1); | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 8 2]); | |
| plot(0:199,dhf1), grid on; | |
| saveas(gcf,'dconvdatafilter.png') | |
| % Conv data and differentiated filter | |
| dhf = conv(f,dh,'same'); | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 8 2]); | |
| plot(0:200,dhf), grid on; | |
| saveas(gcf,'convdatadfilter.png') | |
| % Conv data and second order differentiated filter | |
| d2hf = conv(f,d2h,'same'); | |
| fig = figure; | |
| set(fig, 'PaperUnits', 'inches'); | |
| set(fig, 'PaperPosition', [0 0 8 2]); | |
| plot(0:200,d2hf), grid on; | |
| saveas(gcf,'convdatad2filter.png') |
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