Images

Colour depths and PPI

Picture A

Big image

Picture B

Big image

Binary

Every pixel in an image is represented in binary so the computer can read and display it. If an image is 5 pixels by 3 pixels, it would be something like:

10 10 11 00 11

10 01 11 01 11

00 00 11 01 11


These numbers represent pixels in the image. Each binary number represents a colour, which is decided by the colour depth...

Colour depth and metadata

The colour depth is how many colours the image has available. The higher the colour depth, the wider the range of colours is. Picture A has a colour depth of 2, whereas picture B has a colour depth of 32. As you can see, there are many more colours in picture B than there are in picture A. Colour depths are normally 216, which means that there are 216 available colours. The lower the colour depth, the lower quality the picture.


The colour depth is included in the metadata, which includes data about the file. The height and width are also included in the metadata. The metadata is needed because without it, the computer wouldn't know how to display the image, and therefore the image couldn't be displayed, rather defeating the point of an image.

File size

The file size is affected by the colour depth, dimensions and PPI (Pixels Per Inch). Picture A has a lower file size because it has a much lower colour depth and PPI. The data that is stored is much less, because there are much less pixels to worry about.