Tone curve function explanation
I have done a lot of searching about tone curves, and I understand what it does but not how I would go about creating it.
I want to display the tone curve of an image, and update the tone curve when I make adjustments to the image.
From what I have searched, the tone curve shows the original (input) value along the x axis against the resulting (output) value along the y axis.
The tone curve for the original image is a straight line from the bottom left to the bottom right.
My first thought was that along the x axis is just the histogram of the image, when the image is adjusted then the tone curve displays the difference +ve or -ve from the diagonal line showing changes between the original histogram and the current histogram?
Could anyone shed some light on how I would actually go about displaying the tone curve and if I have the right idea.