Legacy ImageMagick Discussions Archive

Which GPU filter are you using? From the page you linked, https://github.com/BradLarson/GPUImage :
GPUImageToneCurveFilter: Adjusts the colors of an image based on spline curves for each color channel.
So the output will be created by joining together a number of spline curves.

By contrast, the ...

I'm currently using GPUimage to change the color(RGB) channels of images to produce "filter like" effects. The values I use for GPUImage are the X,Y values of the points of the color curve tool in photoshop. So for example I might have these points:

Photoshop curve tool. Please note that the image ...