# Numeric derivation from iminfo

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Life is Wonderful on 8 Feb 2023
Commented: Life is Wonderful on 14 Feb 2023
Hi there,
I'm trying to solve the following problem with the iminfo function using info structure for a jpg and png format
out_perf = pixel_rate_MHz * plane_source_bytes_per_pixel * memory_value_microseconds
where
pixel_rate_MHz = Horizontal_Active_Resolution * Vertical_Active_Resolution * Refresh_Rate * (1+ Blanking_Period/100); % need help
plane_source_bytes_per_pixel = ?? % Need help
memory_value_microseconds =?? % Need help
Thank you very much.

Walter Roberson on 8 Feb 2023
unfortunately in practice the large majority of the time, doing this computation is useless. A lot of images do not have the resolution stored, and it is extremely common to find that the stored resolution is 100 if the image was created using Windows software, or 72 if created using Apple: that is, nominal values are filled in that have nothing to do with the actual resolution.
Calculating actual resolution using the content of the images is not possible unless the image contains items of known size.
I notice however that the equations talk about clock rates and similar. Those kinds of calculations are used for calculation of bandwidth requirements or transmission time requirements, and in such situations, the resolution of the images is irrelevant, with the calculation needing to know the size of the image, rows and columns and color panes, and bits per pixel.
Remember, resolution of a pixel is the real world distance between adjacent pixels. If you were to put in a 10:1 magnifying lens then the resolution would get 10 times higher (until you get down to distances comparable to the wavelength of the light) but the sensor still has the same number of pixels and would record 1/10 as large of a space, leading to the same number of pixels. Resolution is not the number of pixels. An electron force microscope might only produce 16 x 16 pixels but the resolution might be in the nanometer range.
Walter Roberson on 14 Feb 2023
according to the article, blank period percent is a characteristic the hardware and is to be looked up in the documentation of the hardware.
You might find it instructive to look at the description of NTSC, with its horizontal retrace and vertical retrace and "front porch" and "back porch". Modern digital hardware does not need all of those but it might need some of them depending on the technology.
Life is Wonderful on 14 Feb 2023
Sure.
Thanks a lot .

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