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I'm an igsce student. I'm taking computer science as an OL subject this year.

Pixels are the small squares which make an image. Inside each pixel there are 3 channels: one for blue, one for green, one for red. The three primary colours from which any other colour can be made. And that's how I imagine it:enter image description here When we say an image is 8-bits we actually mean that for each channel (in one pixel) of green, blue or red there are 8 bits. So green can have 255 shades/intensities/brightness and so on for the rest of the colours.

So even for a 1-bit image, each pixel contains 3 channels one for each of the primary colours. The only difference is that there's only 1 intensity/brightness/quantity for each colour.

So even in 1-bit image the three primary colours still exist so more colours other than black and white can be made by mixing the three colours together, 8 colours to be exact. Why is it said then that a 1-bit image is only black and white?

Manar
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Please read the Wikipedia article 8-bit color.

8-bit color graphics are a method of storing image information in a computer's memory or in an image file, so that each pixel is represented by one 8-bit byte. The maximum number of colors that can be displayed at any one time is 256 or 2⁸.

In other words, the problem is that 8 bits mean that all three primary colors red, green, and blue, are encoded in 8 bits in total. From Wikipedia:

The simplest form of quantization frequently called 8-bit truecolor is to simply assign 3 bits to red, 3 to green and 2 to blue (the human eye is less sensitive to blue light) to create a 3-3-2

Bit    7  6  5  4  3  2  1  0
Data   R  R  R  G  G  G  B  B

8-bit color image, but this process is sub optimal. There could be different groupings of colors that make evenly spreading the colors out inefficient and likely to misrepresent the actual image. Because the color map doesn't need to have every color in it and just needs to accurately represent the more color dense image, an arbitrary color can be assigned to each of the 256 available color 'slots' on the map. [...]

Concluding, 1 bit means that you can have only two states, e.g. black/white.

Ainsley H.
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