Home > Archive > Compression > April 2006 > Calculate minimum compressed file size for a JPEG image
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Calculate minimum compressed file size for a JPEG image
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| libation 2006-04-25, 6:56 pm |
| Hi,
I was wondering if it were possible to calculate what the minimum file
size for a JPEG image would be if you know the dimensions, resolution
and compression settings for the image and if so, how? I'm trying to
work out what the smallest compressed file size a scanned blank page
of known dimensions can be.
Thanks
Chris Armour
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| Thomas Richter 2006-04-25, 6:56 pm |
| Hi,
> I was wondering if it were possible to calculate what the minimum file
> size for a JPEG image would be if you know the dimensions, resolution
> and compression settings for the image and if so, how?
Taking the minimum over all images, or given one specific image?
> I'm trying to
> work out what the smallest compressed file size a scanned blank page
> of known dimensions can be.
That will likely contain some noise. To get the smallest size, you would
need to feed the DCT with coefficients that transform to all zero. This would
be a constant medium grey level of a level that equals the level shift prior
the DCT coefficient. AFAIK, for an 8bpp image a level of 128.
So long,
Thomas
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| Jasen Betts 2006-04-28, 7:55 am |
| On 2006-04-25, libation <chris.armour@gmail.com> wrote:
> Hi,
>
> I was wondering if it were possible to calculate what the minimum file
> size for a JPEG image would be if you know the dimensions, resolution
> and compression settings for the image and if so, how? I'm trying to
> work out what the smallest compressed file size a scanned blank page
> of known dimensions can be.
The Gimp does that reasonably well, so yes.
how? you'd have to look in the source.
Bye.
Jasen
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