Compressing image files has become a necessity due to the constrained space of hard drives, flash disks, and web hosters. This is because a common text file is comparatively smaller than an image file; an 800×600 24 bit color image file will usually take up 1.37 MB of space, and those are just small ones. One of the more popular formats to save a compressed image is JPEG which usually has an extension name of .JPG or .JPEG. It can achieve compression ratios of 10:1 with practically no lose in image quality.
There are two options with which you can compress your JPEG files. They refer to the same thing but are polar opposites of each other. Saving the file at 60% quality will mean a compression of 40%. Depending on the program you use, you will find either of these two options, but the results will always be the same: more quality will mean less compression and vice-versa.
Different programs also have different quality scale. By saving an image at 55 to 60 quality in Photoshop, it will look and have the same file size of other softwares saved at 80%. Also, never get tempted to save an image at 100% quality because this is not the highest possible quality rather it is the mathematical optimization limit, which will give you an unreasonably big file. Save the image at 95% quality for optimal results. This will be enough to prevent loss in quality and will produce the smallest file size for that quality.
Besides those options, some programs such as Paint Shop Pro and Corel Photo Paint allows you to choose the type of image downsampling or subsampling. A subsampling of 4:4:4 means that the image is not subsampled, 4:2:2 is standard subsampling, and 4:1:1 produces the lowest quality downsampling, although rarely used.
Aside from these tools, you can also optimize your image file by changing how the image data is stored . JPEG format is stored in a 8×8 pixel block and by saving the image exactly within the image block, it will produce a sharper image and save you a couple of MBs in the process. You will be able to see this if you set the JPEG quality parameter to low.
When a JPEG image is saved the image will be divided into blocks of 8×8 pixels. Each block will then be optimized independently. The image will look fuzzy if it does not fit exactly into the pixel block. Also, by adjusting the image right into the pixel blocks, you are decreasing the number of 8×8 blocks used up by the file. This way, the file will be save in to smaller size.
By doing these tips, you will be able to save up on disk space or web space when uploading your images. Every KB is precious due to the limited space it offers, and by effectively decreasing the size, even by a couple of KBs and not sacrifice any quality is well worth it.
