Images on the computer screen are comprised of tiny pixels. Each pixel is a mixture of red, green, and blue. The picture above from Bryce Canyon National Park is comprised of 287 rows of pixels. Each row has 424 pixels. To see just the red component move your mouse over the red icon above; to see just the green component move your mouse over the green icon above; to see just the blue component move your mouse over the blue icon above; and to see a black-and-white version obtained by averaging the red, green, and blue components move your mouse over the black-and-white icon above.
The intensity of each of the colors red, green, and blue for each pixel is usually represented either by an integer between 0 and 255 or by a real number between 0 and 1. In the first system the color black is represented by (0, 0, 0) and the color white by (255, 255, 255). In the second system the color black is represented by (0, 0, 0) and the color white by (1, 1, 1). More precisely (255, 255, 255) in the first system and (1, 1, 1) in the second system represent the brightest white that is produced by a particular display device.
We begin by exploring some of the capabilities of Color_Play. This applet takes an image and produces a new image pixel-by-pixel. The color component of each pixel of the new image is computed by a formula of the form:
For example, suppose you wanted to produce a new picture isolating just the red component of the original picture. You would use the following three formulas:
new red = 0 + 1 * (original red) + 0 * (original green) + 0 * (original blue) new green = 0 + 0 * (original red) + 0 * (original green) + 0 * (original blue) new blue = 0 + 0 * (original red) + 0 * (original green) + 0 * (original blue) |
Fill in the 12 entries in the form below using the three formulas above. Then press the Make new picture with transformed colors button to produce a picture isolating just the red component of the Bryce Canyon picture. Depending on the speed of your computer it make take as much as one minute to produce the new picture. The new picture will appear in a new window, so that you can compare the new picture with the original.
To display shades of grey we use the same value for the red, green, and blue components. The three formulas below will convert a color picture to a monochrome picture.
new red = 0 + .333 * (original red) + .333 * (original green) + .333 * (original blue) new green = 0 + .333 * (original red) + .333 * (original green) + .333 * (original blue) new blue = 0 + .333 * (original red) + .333 * (original green) + .333 * (original blue) |
Try it.
You can produce a black-and-white negative using the three formulas below.
new red = 1 - .333 * (original red) - .333 * (original green) - .333 * (original blue) new green = 1 - .333 * (original red) - .333 * (original green) - .333 * (original blue) new blue = 1 - .333 * (original red) - .333 * (original green) - .333 * (original blue) |
Try it.
Experiment 1: Exchange the colors red and blue.
Experiment 2: Transform red to green; green to blue; and blue to red.
Experiment 3: Produce a color negative.
Experiment 4: Make a new picture that preserves the colors of the original but makes them all darker.
Experiment 5: Make a new picture that preserves the colors of the original but makes them all lighter.
Experiment 6: Make a new picture showing what Bryce Canyon would look like near sunset.
Note: different people may produce different answers for some of these experiments. Be prepared to explain how you interpreted the instructions for each experiment and why you chose that interpretation.
Experiment 7: Be creative. Produce a weird and wild rendition of the Bryce Canyon picture.