An image file is an array of numbers. For a black and white image, it’s a 2 dimensional array with lightness values. For each (x,y) coordinate in the image, there is a single number representing the lightness of the pixel.
Here’s a simple example of what data might look like for a 3×3 pixel image:
| Lightness | x = 0 | x = 1 | x = 2 |
| y = 0 | 0 | 85 | 170 |
| y = 1 | 170 | 255 | 85 |
| y = 2 | 85 | 170 | 0 |
A zoomed in version of this tiny image looks like this:
The black pixels have a lightness of zero, and the white pixel in the middle has a lightness of 255. The values in between represent light or dark shades of gray.
A color image has more data. Instead of storing a single number for each pixel on the grid, it stores three numbers representing RGB values (red, green, blue).
| (R, G, B) | x = 0 | x = 1 | x = 2 |
| y = 0 | (255, 0, 0) | (0, 255, 0) | (0, 0, 255) |
| y = 1 | (255, 255, 0) | (255, 255, 255) | (255, 0, 255) |
| y = 2 | (0, 0, 0) | (128, 128, 128) | (0, 255, 255) |
Color images are 3 dimensional arrays.
The three dimensions are x, y, and color. For each (x,y) pixel value, there is a one dimensional color array containing three values.
You can use a Color Picker to get the RGB values for a certain color, or to figure out what color a certain combination of RGB values would create.