Image editing

Besides sharpening some image editing options for adjusting brightness/gamma/contrast/color balance etc. can be useful in practice. Of course, the situation permits only a limited feature set. Extensive image manipulation must be done separately with one of the many available graphics programs.

The plugin comes with a small graphical editor which operates analog to the 'curves' tool in Gimp. It can be started by clicking the 'ImgEd'. The green state of the button signals activeness. As long as the image editor is open, images will be displayed (and saved!) in a modified version acc. to the current curve adjustments. Clicking the 'ImgEd' button again closes the editor, and images will come out without modifications again.
The transformation curve(s) can be adjusted with the mouse pointer (left mouse button pressed), releasing the mouse button triggers application of the current transformation to the image.

Linear mode



Left-clicking with the mouse pointer in one of the two end points allows to modify the transformation curve in a linear way, for increasing or decreasing brightness and/or clippping.

Gamma mode



Left-clicking with the mouse pointer into the area between the end points activates the gamma curve mode. The gamma curve can be adjusted further by clicking with the pointer on the curve and dragging it into the preferred form. Limits are imposed on the curve adjustment, to avoid undefined states. The gamma transformation is only performed in the region between the lower and upper end or clipping point, and it can optionally be applied on top of a linear curve modification.

Color balance

When working in color mode, each color channel curve can be edited separately, plus a common value curve acting on all channels.

State of development

Adjusting the gamma curve with the mouse pointer is of course over-determined, as it uses 2 degrees of freedom (x,y) for only one parameter (gamma). But displaying the curve is more intuitive than showing just a slider value, and, furthermore, the aim was to implement a framework for optional future development of more complex transformation curve formats.