What is the best method to compress the size of image using photoshop?
For what purpose ? When you need generalpression to decrease a PSD 's file size just try zipping it ( Compress italic in File italic menu on Mac). For creating web best. There's no better italic with JPEG PNG or GIF 3 each format has its benefits depending on the kind of contains just a few 'flat' colors (like diagrams logos graphs etc.) then GIF or PNG 8-bit with a strict amount of colors might prove best. Photo's images with blends gradients shadows or anything else or mixed ? JPEG is your friend.
How can I compress an image size on iOS?
Thepression is performed on anyputer running software (or programs). So you need software (or programs) that runs on iOS. Search goggle for something like best free Resize the under a new Folder or Filename as a JPG or PNG Good luck.
How do I compress pictures without losing quality?
Think about it Reducing the size of an had detail on that scale to begin with. However you may not notice the missing resolution. If the s by zooming into them to see a part of the resolution without losing any quality is by starting with an resolution aren better than others. Books and PhD dissertation have been written studying various ways to do this. You didn say whether you are looking for a personal service or a free web site some ready made free or paid software or aputer algorithm. Rather than trying to repeat the extensive literature about this let me just point you in the right direction. Here is a good StackOverflow Q&A on this topic What is the best -downscaling-algorithm-quality-wise The consensus of that discussion is that the Lanczos method is considered the best by many. The ImageMagick website has a detailed articleparing these methods at Resampling Filters #unix Windows #macosx iOS interpolation software.
Can you describe lossy and lossless compression techniques and how they might affect image size and quality?
Lossless As the name describes there is no quality loss. The decoded quality loss which is controlled by the desiredpression. The morepression the worst the quality. However the goal is to have perceptually losslesspression. Obviously lossypression gives you smaller files than lossless.