imgproxy has a specific processing pipeline tuned for maximum performance. When you process an image with imgproxy, it does the following:
- If the source image format allows shrink-on-load, imgproxy uses it to quickly resize the image to the size that is closest to desired;
- If it is needed to resize an image with an alpha-channel, imgproxy premultiplies one to handle alpha correctly;
- imgproxy resizes the image to the desired size;
- If the image colorspace need to be fixed, imgproxy fixes it;
- imgproxy rotates/flip the image according to EXIF metadata;
- imgproxy crops the image using specified gravity;
- imgproxy fills the image background if the background color was specified;
- imgproxy applies gaussian blur and sharpen filters;
- imgproxy adds watermark if one was specified;
- And finally, imgproxy saves the image to the desired format.
This pipeline with using sequential access to source image data allows to significantly reduce memory and CPU usage — one of the reasons imgproxy is so performant.