Try the new photo editor at the link below:
Change the contrast of the photos online
The new photo editor supports batch processing of images.
There will be an image processing queue. Add new filters (bottom)
To change the contrast of the photo, upload the necessary files, and specify contrast settings (value greater than 0 - increase contrast, less than 0 - decrease). After that, click the "Download" button and download the processed images.
You can also add additional effects (brightness, saturation, etc.) to improve the photo.
Image processing service