Activity 3 - Scilab Basics

Similar to activity 2, I was able start with activity 3 last August 24 for the same reasons. Since ma'am was no able to attend class that time, I chose to work on the activities in our laboratory and work on it independently.

Activity 3 involves the use of Scilab, which is a very powerful programming language advantageous for matrix calculations. The activity serves as an introduction to Scilab employing some of its basic commands, which shall be vital since the activities will become more avanced as the semester progresses. 

In this activity, we were tasked to synthesize images using Scilab. Images are represented as matrices so we exploit the capabilities of Scilab to do this. A sample code was given which produces a centered circular aperture as shown below.

Centered circular aperture

The sample code was very helpful in serving as a basis on how to produce the listed target images, which were: centered square aperture, sinusoid along the x (corrogated roof-like pattern), grating along the x, annulus, circular aperture with a Gaussian transparency, cross, and an ellipse. Of course, as most of the time, I also seeked help from a very good friend -- Google. I searched for some of the commands and syntax of Scilab, which mostly led me to the help.scilab.org website. The synthesized images are shown below

Centered square aperture

Sinusoid along the x-axis (corrogated roof-like pattern)

Grating along the x-axis

Annulus

Circular aperture with a Gaussian transparency

Cross

Ellipse

I also tried applying the basic matrix operations to the different matrices corresponding to the images above. These includes addition (+), subtraction (-), multiplication (*), element-wise multiplications (.*). The resulting images are shown below.

Centerd circular aperture + centered square aperture

Circular aperture with Gaussian transparency - annulus

Annulus * centered circular aperture

Sinusoid along the x-acis .* grating along the x-axis

 It is interesting to note that when addition, subtraction, and element-wise multiplication were performed, the resulting images still showcased the general apperance of its constituents. Take for example the image when both the centered circular and square apertures were added. We can still see a circular and square pattern in the image. The same goes for annulus * centered circular aperture and sinusoid along the x-axis .* grating along the x-axis. On the other hand, when matrix multiplication was performed, the resulting image was entirely different from the multiplied matrices. Circular profiles, which are the main features of the constituents, are not observable in the resulting image.

Aside from the prescribed images to be synthesized, I also synthesized an image of a pokeball, inspired by the currently trending game Pokemon Go. At first, I thought that the synthesis of this image would be difficult. But due to the symmetry of the image and the similarity of the patterns to the images above, I was able to produce the image as shown below. 

Pokeball

The activity was fun yet very helpful. Having used Scilab last semester just briefly, this activity has helped me to review what I already know about Scilab, learn new things about the language, and further engrave in my mind the things-to-know about Scilab. I am excited about further lessons involving the use of Scilab in a more advanced topic. For this activity, maybe I will give my self a grade of 11. I was able to produce all the listed target images, along with other images employing matrix operations and, in addition, a pokeball. I think that the images are also presented well.

I have included the code which produced the images above, for the reference of those who want to produce such or similar patterns. 

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nx = 100 ; ny = 100 ; x = linspace(-1,1,nx); y = linspace(-1,1,ny); [X,Y] = ndgrid(x,y); // Centered circular aperture r = sqrt(X.^2 + Y.^2); A = zeros(nx,ny); A(find(r<0.7)) = 1; f = scf(); grayplot(x,y,A); f.color_map = graycolormap(32); // Centered square aperture B = zeros(nx,ny); B((nx/2)-(nx/4):(nx/2)+(nx/4), (ny/2)-(ny/4):(ny/2)+(ny/4))=1; f2 = scf(); grayplot(x,y,B); f2.color_map = graycolormap(32); // Sinusoid along the x-direction C = sin(30*X); f3 = scf(); grayplot(x,y,C); f3.color_map = graycolormap(32); // Grating along the x-direction D = zeros(nx,ny); D(:,1:5:100) = 1; f4 = scf(); grayplot(x,y,D); f4.color_map = graycolormap(32); // Annulus r1 = sqrt(X.^2 + Y.^2); E = zeros(nx,ny); E(find(r1>0.3 & r1<0.7)) = 1; f5 = scf(); grayplot(x,y,E); f5.color_map = graycolormap(32); // Circular aperture with Gaussian transparency r3 = sqrt(X.^2 + Y.^2); F1 = zeros(nx,ny); F1(find(r<0.7))=1 ; F2 = exp(-(X.^2 + Y.^2)/0.05); F = F1.*F2; f6 = scf(); grayplot(x,y,F); f6.color_map = graycolormap(32); // Ellipse a = max(x)/2; b = max(y)/4 ; r4 = (X.^2 / a^2) + (Y.^2 / b^2); G = zeros(nx,ny); G(find(r4<1)) = 1; f7 = scf(); grayplot(x,y,G); f7.color_map = graycolormap(32); // Cross H = zeros(nx,ny); H((nx/2)-(nx/4):(nx/2)+(nx/4),(ny/2)-(ny/8):(ny/2)+(ny/8)) = 1; H((nx/2)-(nx/8):(nx/2)+(nx/8),(ny/2)-(ny/4):(ny/2)+(ny/4)) = 1; f8 = scf(); grayplot(x,y,H); f8.color_map = graycolormap(32); // Circular aperture + square aperture f9 = scf(); grayplot(x,y,A+B); f9.color_map = graycolormap(32); // Sinusoid along the x direction .* grating along the x f10 = scf(); grayplot(x,y,C.*D); f10.color_map = graycolormap(32); // Annulus * circular aperture f11 = scf(); grayplot(x,y,E*A); f11.color_map = graycolormap(32); // Pokeball r5 = sqrt(X.^2 + Y.^2); P = zeros(nx,ny); P(find(r<0.2))=1; P(find(r>0.3 & r<0.8))=1; P(:,48:53) = 0; P(find(r<0.2))=1; P(find(r>0.1 & r<0.13))=0; f12 = scf(); grayplot(x,y,P); f12.color_map = graycolormap(32);