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Filesize of an image

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chitresh on 22 Nov 2013
Commented: Laurent on 22 Nov 2013
i gone through some doc where i know the formula for an image filesize that is filesize = (height*width*bitdepth)/8 ;
i read an image file with imfinfo command it gives Filename: [1x50 char] FileModDate: '21-Nov-2013 18:42:02' FileSize: 174421 Format: 'jpg' FormatVersion: '' Width: 728 Height: 485 BitDepth: 24 ColorType: 'truecolor' FormatSignature: '' NumberOfSamples: 3 CodingMethod: 'Huffman' CodingProcess: 'Sequential' Comment: {}
so according to this file size is 174421 but according to formula its coming (728*485*24)/8 = 1059240
so what is the file size acualy is of an image

Accepted Answer

Laurent on 22 Nov 2013
Your image is stored as a jpg-file, which usually means that the image is compressed. In this case using the Huffman method (CodingMethod) (for more info see ).
Compressing an image results in a smaller file than you would expect based on the size on the image. This is useful to save space on a hard drive.
When you open the file it will be decompressed and usually it will be stored uncompressed in your memory (RAM). Then it will occupy 1059240 bytes.
Laurent on 22 Nov 2013
Yes, so approximately 6:1.

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