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We're now at the point that we can start Sketching and Processing. Now normally when you learn a new programming language, you begin by writing some code and getting some text output, like "Hello, World!" Now something we are perfectly capable of doing in Processing like this, and once I have that I can press Run by clicking on this button or I can press Ctrl+R on the keyboard for a PC or Cmd+R on a Mac. And what I get is an empty display window, because I have no graphical commands.
There you see right at the bottom in the message box, I have "Hello, World!" So I've successfully created my first Processing program. But the beauty of Processing is that it's able to do graphical output from the text. And so the simplest way to start in Processing is to draw some basic shapes, also known as primitive shapes or geometric primitives. Now not only is this a good place to start for learning Processing, it's also good Processing for data visualization, as the shapes form the basis of most visualizations. So I am going to comeback to my Sketch here and I'm going to set a Sketch Window size.
To do that I type size and then in parentheses () I put the number of pixels wide and the number of pixels tall, I will do 600 x 200 and then I put a semicolon (;) at the end to say I am finished with that particular comment. Now you see by the way that Processing is coloring the commands, print line and size are recognized known commands in Processing, so put some in orange color. And now if I click Run, you will see that I have a larger display window, it's still empty, because I am not putting anything in it, but it is 600 x 200 pixels, I'll close that now.
Now one important thing to understand if you're not familiar with programming is that like most other programs, the counting for pixels in a window starts at 0, 0 like the graphs you're used to, but they start at the top left and the x-coordinates increase as you go to the right, but the y coordinates increase as you go down. There are a lot of good reasons for this, but it can be a little disorienting if you're not accustomed to it. Now there are a couple things that I want to do here that I always do when I start a new window.
First I set the size of the window and then I turn on anti-aliasing, which makes things a little smoother. In fact, the command for that in Processing is smooth and then I have to put opening and closing parentheses () and a semicolon (;). Now the reason I have the parentheses () with nothing in them is because functions require arguments, smooth is a function and the empty parentheses () indicate that while it is a function there are no arguments or extra information needed for it to do it. However, it does have to have them, so I put smooth open and close parenthesis () then I finish with the semicolon (;).
Now if I want to draw a circle, I'm going to show you a lot more about this, but I can do it like this, in Processing there is not a built in circle command, but there is a ellipse command, and if you want to make a circle you just make them the same height width. So what I am going to do is I am going to type ellipse then in the parenthesis (). I have to first locate the ellipse, I'll put it right in the middle so that's 300 pixels over and 100 pixels down, then I pick the size of the ellipse, this is diameter by the way. So I am going to put it 100 wide and 100 tall, close the parenthesis, semicolon (;) and now if I press Ctrl+R on a PC or Cmd+R on a Mac to run the Sketch and I get my circle.
And in one sense this is the "Hello, World!" For Processing, because Processing is designed for graphical output and that's what I have here first. I am going to close this again, now one of the things I can alter in my sketch very easily is the background color. By default the sketch is gray. Let's take another quick look at it. I have a middling gray background and have a white circle with a black outline if I want to change the color of the background all I have to do is enter the function background all lowercase. Now please make sure if you enter that command, to enter it before you draw the circle or the background will cover up the ellipse. I've mentioned before that the order of operations matters in Processing.
So I am going to type in background and in the parenthesis () I get to put the code for the color I want. Now if I put a single number here, it's going to give a grayscale, it goes from 0 for Black up to white. Now it is not 100 at the top, it's 255, that's because it's an 8-bit Color Scheme. If you're not familiar with this, it can seem a little disoriented to go up to 255, but it has to do with binary numbers, and it's a very common approach with computer graphics. If I want it to be black, I just put in 0. I close the parenthesis, put a semicolon (;) and I can hit Run.
And now I have a black background for my white circle. On the other hand, if I want a white background, I can change the 0 to the maximum value of 255. Now have a white background with my white circle. Finally, if I want it to be a color background, I can use a three component coding system, it's the RGB, Red Green Blue, system that's common in Computer Graphics. In this particular case I'll just make it Red by putting the Red value at its maximum, and the Green and the Blue components at their minimum.
Please note, I have got the three numbers, they are separated with commas (,) and they're still in the parenthesis () and finish with the semicolon (;) now I hit Run and have a brilliant red background with my white circle. Now there's just one more thing I want to show you in this particular sketch and that's how to add comments to a sketch. I personally find it's very useful to comment to indicate what you're doing. Now, I generally comment more than other people, in my own work I attend to comment every single line, which is probably excessive, but makes it very easy to read the code.
I will not be commenting this much in this course, because I'll be describing in words to you, what each program is as I go through. However, I'm going to add a comment right here, by going to the top I'm going to click a print line and move that down a little bit. Now I am going to add a comment with the name of this file, I find that to be a helpful thing in general. Now because this is going to be a single line comment, what I do is I put two slashes //. These are the slashes that are down by the question mark (?). Then I put a space here and then I can put the name of this particular file.
And that helps me identify it in case I have got several files open. And you can see comments are by default colored gray in Processing, and if I want to add a comment somewhere else, I can put one for instance, after a line of code. Right here I can put a couple of spaces with two slashes and put Red background. And that's one way of keeping track of what I'm doing in this. Now if I'm going to have a comment that is more than one line long, for instance, I want to put an entire paragraph in, the way to do that is with a (/*).
So I'll come down to the bottom here, I put (/*), I can go to the next line if I want. This is a very long comment. Once I have the entire comment in, I can finish with an (*/) and now Processing knows that I'm done with the entire comment. Again, this can be very helpful, both if you intend on sharing your sketches with other people and for helping you reconstitute the sketch if you come back to it at a later time. Then as a final note, each sketch will be saved in the folder with the exact same name as the sketch.
So if you go and manually change the name of the folder, you need to make sure that the sketch has the exact same name, the only exception is that the sketch will have the .pde Extension on the file, and with that we're ready get drawing in Processing
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