Image Code

In this section, we'll look at simple code to load and manipulate a digital image. Here we'll just manipulate one pixel at a time. In the next section, scaling up to operate on thousands of pixels at a time.

x.png

• x.png -- tiny example image (10 x 10)
• PNG format, like JPG

The image "x.png" is very simple -- it's a very small black square with a white "x" at its center. PNG (Portable Network Graphics) is a image format, like JPG. Here is x.png:

x.png Code Example

• Three line program
• image = new SimpleImage("x.png"); -- load into variable
• image.setZoom(20); -- set zoom option to 20 (10, 20, 30, ... whatever)
• print(image); -- print image to the right, as usual
• Zoom: each pixel shown 20x size here

Our first image code example loads the x.png image and prints it. Run the code to see what it does. Try changing the image.setZoom(20) to use the number 10 or 30 instead.

image = new SimpleImage("x.png"); image.setZoom(20); print(image);

pixel.setRed(255) Example

• pixel = image.getPixel(0, 0); -- upper left pixel
• pixel.setRed(255); -- set red value of that pixel

image = new SimpleImage("x.png"); image.setZoom(20); pixel = image.getPixel(0, 0); pixel.setRed(255); print(image);

Pixel Set Red/Green/Blue Functions

• pixel.setRed(number); -- set the red value of the pixel to be the given number (0..255)
• pixel.setGreen(number); -- set the green value
• pixel.setBlue(number); -- set the blue value

Aside: Image Functions Reference

For later reference, there is a separate image functions reference page which lists in one place the image functions such as pixel.setRed(number) we are using here.

Experiments On Pixel (0, 0)

To see how image.getPixel(x, y) and pixel.setRed(number) etc. work, we'll try the experiments listed below (use the "show" button to see the solution code).

image = new SimpleImage("x.png"); image.setZoom(20); pixel = image.getPixel(0, 0); pixel.setRed(255); print(image);

Example Problems	Solution
Set pixel (0, 0) to be green.	show pixel = image.getPixel(0, 0); pixel.setGreen(255);
Set pixel (0, 0) to be yellow.	show pixel = image.getPixel(0, 0); pixel.setRed(255); // idea: set red and green to 255 pixel.setGreen(255);
Set pixel (1, 0) to be yellow. Where is that pixel?	show pixel = image.getPixel(1, 0); pixel.setRed(255); pixel.setGreen(255); // Calling getPixel(1, 0) edits the pixel // one to the right of pixel (0, 0).
Set pixel (0, 0) to white.	show pixel = image.getPixel(0, 0); pixel.setRed(255); pixel.setGreen(255); pixel.setBlue(255);
Set pixel (0, 0) to be dark yellow -- set the necessary colors to 150 instead of 255.	show pixel = image.getPixel(0, 0); pixel.setRed(150); pixel.setGreen(150);
Set pixel (0, 0) to be a light, pastel red.	show pixel = image.getPixel(0, 0); pixel.setRed(255); pixel.setGreen(200); pixel.setBlue(200); // Set red at 255, green and blue equal but lower.

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