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Re: how to define size of image in common case [message #71659]

Tue, 06 July 2010 04:16

jeanh
Messages: 79
Registered: November 2009

Member

On 06/07/2010 12:32 AM, skymaxwell@gmail.com wrote:
> how to define size of image (in bytes) in common case ?
>
> I use the following formula
>
> V=(image_size_x/pixel_size_x)*(image_size_y/pixel_size_y)*Nb ands*10E-6
>
> image_size_x, image_size_y - dimensions of image (in meters)
> pixel_size_x, pixel_size_y - spatial resolution (in meters)
>
> Unfortunately, for some images it's wrong - it doesn't match with file
> size.
> Why ?
>
> Thanks

Hi,
the formula is : number of pixels * weight of each pixels.
So, if the pixels are in Byte, each pixel is 8 bits, integers -> 16
bits, floats -> 32 bits etc

Also, some images have their header embedded... other formats use some
compression

Jean

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