1. Preview image: This image displays a quick preview of the mosaic image file that will be generated. It is not a final rendering, but a close match to what the final image will look like.
2. Transparency: this sets the transparency level of the main mosaic image. 100% means the image is fully opaque (tiles will not show), and 0% is fully transparent (main mosaic image will not show). Choose a value that suits your taste for a generated final image, usually a 50-65% value works best for most images.
3. Grid Size: allows you to define the mosaic grid size (number of tiles across x number of tiles down). The larger the grid size, the more time it will take to generate the mosaic photo, and the smaller the size of the tile photos.
4. Spacing: this is the space to leave between tile photos in pixels, you can choose a number between 0 to 5.
5. Cancel/Reset: This button toggles between Reset and Cancel depending on whether an image generation is in progress. The Reset button clears all settings back to defaults, while the Cancel button allows you to abort an image generation that's in process.
Progress bar: this will show you current progress of the image generation, as well as an estimate of the time remaining. Please keep in mind that the time remaining estimate depends on a lot of factors including the which device you're running the app on (iPhone 4 will take considerably longer than an iPhone 4S).