As an example, you might upload a high-resolution image with a 4:3 aspect ratio, and display it scaled down, square cropped, or black-and-white (or any combination of these effects). The core software provides a way to do this efficiently:
- Configure an image style with the desired effects on the Image styles page (admin/config/media/image-styles).
- The effects will be applied the first time a particular image is requested in that style.
- The resulting image is saved.
- The next time that same style is requested, the saved image is retrieved without the need to recalculate the effects.
The core software provides several effects that you can use to define styles; others may be provided by contributed modules.
Visit the Image styles page via the Manage administrative menu, navigate to Configuration > Media > Image styles (admin/config/media/image-styles) to see the image styles that are defined by default.