What is color space in images
When I create thumbnails of images or when I scale them, I utilize several parameters and not just the size.
This has to do with the color space of the image. What am I talking about?
There are two ways in which the information of an image is saved.
The first way is the linear scale. Every photo-receptor in a camera saves a certain value, which means if it is getting a light value at the half of it, it saves a 0.5 or a 50% value of light received.
On this scale a middle gray would be all pixels with a floating value of 0.5.
But linear color is not the way we perceive color. For us middle-gray is more like 0.18, not 0.5. Normally for us an 18% gray is considered “middle gray”.
A long time ago most image editors did not take any of this into consideration, even photoshop used to ignore it. It is from that time that I began using different algorithms for image scaling. I continue utilizing the same parameters, but this is the reason why a simple “convert” has the extra parameters.
I am not going into details, it is a wide subject; or talking as things such as Lankzos resampling that I use, but this is the reason that is being used, taking into consideration our perception of light so a scaled image gives the same “feeling” seeing it smaller.
You can read more about color space at: https://en.wikipedia.org/wiki/Color_space