Reshade!

TinyPNG uses smart lossy compression techniques to reduce the file size of your PNG files. By selectively decreasing the number of colours 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!

JPEGmini is a patent-pending photo recompression technology, which significantly reduces the size of photographs without affecting their perceptual quality. The technology works in the domain of baseline JPEG, resulting in files that are fully compatible with any browser, photo software or device that support the standard JPEG format.

BenVista PhotoZoom Pro 5 is a software solution for enlarging and downsizing digital photos and graphics.

Light Image Resizer, previously called VSO Image Resizer, is a shareware resize image software. With it you can create e-mail friendly versions of your images, load them faster, move them easily from folder to folder, change their format, edit large numbers of image files/batch image resize and thus save space on your hard drive. Using high resolution 1600x1200 for creating wallpaper or file-sharing you can save your memory. Light Image Resizer can also change file names using a template and you can add your own watermark with transparency support. Light Image Resizer is integrated into the Windows explorer shell, right click on your pictures and start working on your pictures ! »

SmillaEnlarger is an open-source and portable application designed to help you intensively massage an image enlargement to keep it from looking jagged and filled with artifacts. You can select the level of zoom using the zoom slider and the location of the zoom via the selection box.

Photo Size Optimizer for Mac:

Enlarge photos up to 1000%. Get the highest quality photo enlargements with Genuine Fractals® technology—patented, fractal-based interpolation algorithms—that quickly enlarge your images without loss of sharpness or detail.

Shrink O'Matic is an AIR application to easily (batch) resize (shrink) images. It handles JPGs, GIFs and PNGs.

PhotoResize is a simple tool for very fast batch resizing of photos and pictures in JPEG format. Beyond simple options however, Picture Resizer also contains support for seam-carving (changing size while preserving content), image sharpening, metadata, and other options.

Stoik Smart Resizer - Reduce and Enlarge Images!

HQ Photo Enlarger is a program that produces enlargements dramatically sharper than other software.

If you want a lightweight image editor that you can use to perform basic editing tasks such as cropping, renaming, resizing and even applying watermarks to your pictures, then consider rEASYze. You can work with single or multiple images simultaneously.

Lossless Photo Squeezer for Mac is a professional image size compressor which will reduce your PNG, JPEG and GIF photos and images size with LOSSLESS quality. You can optimize all your photos to save much hard drive space, web space and share full-resolution photos online more faster.

IMAGEmini, a powerful photo resizer and optimizer, allows you to optimize all your photos by 80% ~ 20% comparing to their originals while keeping their original resolution, quality and png, jpg, gif formats. With IMAGEmini, you can save huge space and share full-resolution photos with your friends much faster.

WinLep is a software that compresses JPG images to LEP. WinLep compresses JPEG and decompresses LEP, moreover it can display JPEG and LEP compressed files. Lepton is a lossless open source algorithm dcapable of compressing images at 5 MB/s and decompressing them at 15 MB/s. This compression format allows the compression of JPEG images saving on average a 22% of size without losing quality in the process of compression and when it is decompressed the image is exactly the original one. WinLep takes advantage of these qualities to offer a fast and lossless quality compressor/decompressor. »