Lossless refers to a compression scheme wherein the image is pixel-by-pixel identical to the original image after its is decompressed.
An example is the PNG (portable network graphics) format.
An example is the PNG (portable network graphics) format.
As it is a lossless format, it has a distinct advantage of having no decrease in quality or detail upon compression. For instance, a radiologist looking at a PNG image never needs to worry about insufficient resolution in the image for his diagnosis.
However, this comes with the disadvantage of smaller compression ratios, or relatively larger size after compression, compared to lossy formats. For instance, PNG images typically have a compression ratio (i.e. size of original image/size of compressed image) of approximately 3.35 (Ferni Ukrit et al., 2011). However, this number is only an average, as exact ratios can vary depending on characteristics of the picture being compressed, like the number of grey levels, colours, or detail.
However, this comes with the disadvantage of smaller compression ratios, or relatively larger size after compression, compared to lossy formats. For instance, PNG images typically have a compression ratio (i.e. size of original image/size of compressed image) of approximately 3.35 (Ferni Ukrit et al., 2011). However, this number is only an average, as exact ratios can vary depending on characteristics of the picture being compressed, like the number of grey levels, colours, or detail.