MagickContrastStretchImage question

[sideralarts]

Greetings,

I am trying to contrast correct a greyscale image to get some details to appear a little sharper. Currently I create my wand and give it the following command:

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MagickContrastStretchImage(image_wand, 0.8, 0.9);

The reason I am posting here is no matter what values I give for the black point and the white point the image never seems to change. When I run

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MagickGetImageChannelRange(image_wand, GrayChannel,&min, &max);

I get that the minimum is 0 and the maximum is 65535. The image I am giving it is a .jpg and I am outputting the contrast into another .jpg file without changing any other setting in my program.

My question is am I using the function correctly? I am having a hard time getting values to give my any change at all, so any advice would be appreciated.