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Here is the definition which I read from the net source

1st is

Midtone: Situated between the darkest tone (Black), and the brightest tone (White). For a 24 bit colour image, this occurs when Red = Green = Blue = 128.

and the other is

Tones created by dots between 30% and 70% of coverage

and

Midtone also refers to the range of colors that aren't mixed with black (the shadows) or white (the highlights).

What i got from these definition is that the pixels whose values are 0 or 255 we should adjust them to 128 . Am i taking the definition right ? I don't want to use the way of Histogram Equalization as according to my knowledge its also use for brightness of image

I want to perform the function like below , like i want to perform this function only in RGB in C++ but i don't know the actual role of midtones and what they perform in the image

enter image description here

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Could you please provide a specific question? You're generally stating your intentions, but it's a bit difficult to be sure.. –  CuriousWebDeveloper Apr 29 at 10:40
    
@JonathanTodd I actually want to perform that type of action in opencv c++ , but i am very new to photoshop so i want to understand what these functions does , as i already reading their tutorials but didn't understand –  ARG Apr 29 at 10:42
    
That's ok, there is no problem with that, it's just that we need an actual question to provide the right answer for you. Could you just reword that last part into an exact, specific question? –  CuriousWebDeveloper Apr 29 at 10:43
    
@JonathanTodd I tried my best to make it better understandable for community –  ARG Apr 29 at 10:45
    
You're using the words "what if", but that doesn't give us a detailed question that we can answer for you. Provide more detail about exactly what you want to know, and we'll be happy to help you! –  CuriousWebDeveloper Apr 29 at 10:45

1 Answer 1

up vote 1 down vote accepted

If you want to understand what “shadows”, “midtones” and “highlights” are and what they do, then, at first you should take a look at the image below without thinking about numbers (at least for now :}).

Public Domain image by Kurt Clark

The darkest colours in this image—like the upper portion of the background or the shadow under the car—are “shadows”. The brightest—e.g. light reflexes on chromed parts—are “highlights”. All the rest is “midtones”—tones between “shadows” and “highlights”. So far, so good :}.

Terms like “shadows”, “midtones” and “highlights” are convenient because they are intuitively understandable. For the same reason, we use colour models like HSL or Lab. “Shadows”, “midtones” and “highlights” then, can be used to quickly identify the portions of image a designer wants to adjust. “Shadows”? Adjust only the darkest regions. “Highlights”? Only the brightest. In that regard “shadows”, “midtones” and “highlights” may be used by any tool, not only “Color Balance”, as means to “point” the colour ranges which are to be acted upon.

“Shadows”, “midtones” and “highlights” can be understood, from the implementer's perspective, as a simple colour ranges (“operation we're about to do will affect only pixels in the given range and no other”). The exact description of these ranges depends on the used colour model. For example, in HSL, we could say that “shadows” are all pixels which have L less than 30%. In RGB, we can use other criteria. Generally, these criteria have to be confirmed experimentally (what feels “intuitive” for the designer). They are formulated in a bit of a heuristic manner, hence the inconsistency of “definitions” you've found.

Once the colour ranges are defined for your case, you may proceed with your image operation. “Selected” pixels will be handed over to your procedure. Any procedure.

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