The image quality barely degrades during compression, and the human eye cannot detect most reductions to quality in lossless compression. Unlike JPG, the PNG file usually compresses with lossless compression. So, when you need to decide between compressing an image and resizing it, think ahead to what you may need that image for in the future - and always keep a copy of your original picture, just in case. PNG files are often used when image quality is a high priority. However, when I am using an image editor such as Gimp and try to save an image as a PNG file, it asks for a compression level ranging between 0 and 9. Jpeg compression definitely gets along better with some details than others. As I understand it, PNG files use lossless compression. Agreed Of particular note in the differences is the engine glow in the 'Earth' image. It can squeeze a file down to 2-10 of original size - but at a cost. The difference images are interesting though - One of the things I did notice was the edges being fuzzier on the jpeg versions, which is clearly displayed in the diffs. To compress your pictures for sending in an e-mail message. To compress your pictures for publication on a Web page, under Resolution, click Web. To compress your pictures for insertion into a document, under Resolution, click Print. The reason jpeg is still widely used, is that its insanely effective. Click the Picture Tools Format tab, and then click Compress Pictures. If you can live with bigger files, png is usually better.
PNG compression is non-destructive, but not as effective. This comes in handy when you need to store your down blanket away for the summer, but you might regret it when winter comes around. View the file at 100 and check what the compression does. The aspect ratio - that is, the dimensions of length and width - will be different than before. With image resizing, think of it as tailoring your blanket from a king size to a twin size. In both cases, you still have the same basic blanket, but one will be slightly fluffier than the other. Or, if you need to make the blanket even smaller, you could remove some of the feathers before packing it up. Think of it like a fluffy down blanket - you can reduce its size by packing it into a box. However, there are critical differences between the two techniques that you should know if you want to set up your image files for success.Īs you learned above, image compression reduces the amount of visual information in a file. Compression and resizing are similar concepts - both can make your file sizes smaller.
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