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Welcome to the REALbasic Developer Magazine Beginner's Corner!
Issue: 1.4 (February/March 2003)
Author: Thomas J. Cunningham
Article Description: No description available.
Article Length (in bytes): 7,967
Starting Page Number: 28
Article Number: 1414
Related Link(s): None
Excerpt of article text...
This month and next month, I will discuss the subject of drawing in REALbasic, commonly known as graphics. Now let me briefly explain what I mean by
drawing . The big picture is thateverything you see on a computer screen has to be drawn to the screen by your computer. This is accomplished by using the tiny little squares that comprise your computer screen. Launch REALbasic, press Command-1, type in the word "graphics," and look through the properties and methods of this class.Pixels ' Resolution
The tiny little squares I mentioned above are called pixels. They are laid out in a grid pattern of rows and columns. The number of rows and columns shown on your computer screen are collectively referred to as your monitor's
resolution . My iMac, at the moment, is set at 1024 pixels by 768 pixels. So I have 1024 pixels from left to right and 768 pixels going up and down my screen, for a total of 786,432 pixels. The physical size of my screen is about 12 inches wide by 9 inches high. So at this screen resolution, I have about 85 pixels for every inch horizontally and vertically.Each of these pixels has a defined location within the screen. In beginning algebra, you were taught to set up a coordinate system that was comprised of a horizontal "X" axis and a vertical "Y" axis. Where these two axes crossed, they were labeled as the origin. And this origin was labeled as zero and zero: positive x values to the right, positive y values moving up.
Computers are laid out using a similar concept, but in a different manner. On a Mac, our origin is at the top, left corner of the screen (or window). The x coordinates are positive moving to the right, but the y coordinates are positive moving
down the screen. On my monitor, the pixel in the middle of the screen would be described as position 512,384. That's 1024/2 and 768/2.It's important to understand this way of describing a position in RB. I strongly suggest that you go out and buy yourself a nice notebook of graph paper. I use this graph paper as a way of wrapping my head around positions in my programs a lot. It will save you many hours of frustration when something you draw on screen doesn't look right or isn't placed where you wanted it to be shown. Figure 1 shows a magnified view of an area six pixels wide by six pixels high and how each of the individual pixel boxes are identified. As an exercise, fill in the pixel x and y positions I have left blank.
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