I created the imager module to enable users to easily view and edit large, high resolution images. Without imager a user must download the image from Drupal to a file, load the file into an image editing application, make the necessary changes, save it back to a file, and then reload the image into Drupal. With imager you can edit the image in-situ and save changes directly back into Drupal.
The images below are sorted by their size - largest to smallest. My favorite image to explore imager's abilities is the "Nebulae Composite" image. Click on the thumbnail to bring up the imager popup and then pan and zoom to different parts of the image. Try increasing the contrast a little and decrease the brightness to bring out the fine structure of the nebulae. Scientists think nebulae are largely the remains of exploded stars, what do you think?
The imager module consists of 2000 lines of php and 3900 lines of JavaScript It operates much like a single page application for all the images displayed on a page. Imager runs on Drupal 7, 8 and 9.
Directions
Left click on an image to bring up the imager popup. The image is displayed in full resolution.
Double click (or press 'X') to exit the imager popup.
Using the mouse and thumbwheel you can zoom, pan, and crop the image. In addition using the buttons on the left you can rotate, change brightness/contrast, and change the hue/saturation/luminosity. The edited image can then be saved back into Drupal as either a new image or it can overwrite the initial image.