OptiPNG and JPEGtran compressors integrated into WOW GALLERY upload with optimal paramaters for major hosting OS. They uses smart lossless compression techniques to reduce the file size of your image files. By selectively decreasing the number of colors in the image, fewer bytes are required to store the data. The effect is nearly invisible but it makes a very large difference in file size!
Different between WordPress upload and WOW GALLERY upload is about 20% - 25% weight
Also you can set optimization quality for each thumbnail in thumbnail generator. Common image optimizations include compression, responsively serving them down based on screen size using <picture>, and resizing them to reduce image decode costs.
Example statistic of potential gallery and image speed savings. Statistics illustrates of efficiency WOW GALLERY compression:
Type of gallery, image
Image Load Speed
Gallery Load Speed
Table of Potential Gallery and Image Speed Savings
2. Pixel Perfect Grid Optimization
Usually images bigger than it must be in grid and cutting by css but WOW GALLERY allows you to create pixel perfect grid by adjusting every single image in grid. All you need it's just select device for optimization and click the magic stick icon in layout mode and it will create all needed thumbnails.
You might say and what? - Your gallery will load faster because it removes all extra pixels.
3. Responsive image serving
WOW GALLERY follows in RICG image serving standard - a client-side solution for delivering alternate image data based on device capabilities to prevent wasted bandwidth and optimize display. It uses <picture> tag. That allows you to set different image sizes in 6 dimensions: Wide - Desktop, Laptop, Tablet Landscape, Tablet, Phone Lanscape and Phone. Devices resolutions based on Desktop, Tablet and Mobile statistics
One more thing...
WOW GALLERY includes only gallery needed CSS files. So you also improve page speed.