How do computers represent pictures?

Answer 1

Computers represent pictures via image files. Image files typically store the information in a grid like format, with each block on the grid being a colored square known as a 'pixel' if you put enough colored blocks next to each other (like, hundreds or thousands) then it starts to look like a picture -- each pixel has its own color and when you put enough of them on the grid the pixels appear as an image rather than a bunch of colored blocks. Everything displayed on a computer screen is a pixel too, and the term 'resolution' is a count of how many pixels are displayed at once, a 1920x1080 screen resolution means that the screen may contain 1920 pixels (colored blocks) from left-to-right and 1080 pixels from top-to-bottom for a whopping 2 million pixels on screen at once (2 megapixels) which results in a screen which can display a lot of finely detailed things at once. Likewise, if you zoomed to 100% on an 8 megapixel image, it would be large enough to occupy 4 1920x1080 computer screens.

Answer 2

It depends on the format, but generally there is a header that contains meta-data, describing the format (regardless of the file extension), the dimensions and the compression that is employed (if any), amongst other details such as time and date, location, etc. The palette of colours may also be included. The program tasked with loading the picture uses this information to determine how the data segment is handled.

An uncompressed bitmap is simply a header followed by a byte sequence denoting the red, green and blue values of each pixel (and possibly an alpha mask value for transparency). Compressed images are more complex, often broken down into a series of frames, however simple lossless compression schemes such as RLE (run-length encoding) store the colour value followed by the number of repetitions of that colour. Thus an image of just one colour (totally black, for instance) can be highly compressed with no loss in quality.

Answer 3

no