Get dimensions of JPEG in C++

Question

I need to get the image dimensions of a JPEG in C++. I'm looking for either a fairly simple way to do it or a smallish library that provides that functionality. I'm working in C++ on OpenVMS, so any external libraries may have to be adapted to compile on our systems - so please don't post me links to big, closed source libraries!

Has anyone come across anything that might do the trick, or understand the JPEG file format (I think I probably mean the JFIF file format here) to tell me how I might go about rolling my own solution?

VonC · Accepted Answer · 2012-11-09T07:00:13.447

15

You have this C function which may extract the relevant data for you.

This is a C routine but should compile fine with C++.
Pass it a normal FILE pointer (from fopen) to the beginning of a jpeg file and two int pointers to be set with the image height and width.

Or you may find in the Boost library a jpeg class which has the right function (From Adobe Generic Image Library).

jpeg_read_dimensions

boost::gil::jpeg_read_dimensions (const char *filename)

Returns the width and height of the JPEG file at the specified location. Throws std::ios_base::failure if the location does not correspond to a valid JPEG file.

edited Nov 09 '12 at 07:00

answered Nov 25 '08 at 12:16

VonC

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Sorry for the delay - just disappeared off to get married! Back at my desk now :-(. I opted for the C routine (though the #defines at the top are HORRIBLE - rewrote those as functions). – Dominic Rodger Dec 16 '08 at 12:40
Congratulation to both of you! – VonC Dec 16 '08 at 12:43
return Many Happy return Many Happy! – EvilTeach Jan 13 '09 at 18:18
@VonC first link is dead, but here's another, looks the same? http://carnage-melon.tom7.org/stuff/jpegsize.html – Ben Nov 09 '12 at 00:09
@Steve Thank you. The first link is fixed. – VonC Nov 09 '12 at 07:00

score 3 · Answer 2 · answered Nov 25 '08 at 12:20

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libjpeg is reasonably small, open source and available on OpenVMS. It's probably quicker to install it than to handle JPEG yourself.

answered Nov 25 '08 at 12:20

Julien Oster

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score 2 · Answer 3 · answered Nov 25 '08 at 12:15

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Maybe libjpeg?

answered Nov 25 '08 at 12:15

activout.se

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score 1 · Answer 4 · answered Nov 25 '08 at 12:18

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You should be able to use this jpeg lib with this patch for OpenVMS

answered Nov 25 '08 at 12:18

carson

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score 1 · Answer 5 · answered Nov 25 '08 at 12:27

No need for full libjpeg library just to get this information (unless you need to do something else with the images). ImageInfo might help you. It is a Java class, but there are ports for other languages, including C++.
As pointed out, Exif might change these information (eg. with orientation setting).

score 0 · Answer 6 · edited Jun 18 '22 at 18:01

You may want to try GDAL library which serves as an abstraction layer for large number of raster data formats, mostly used in geospatial applications for GIS/RS.

GDAL provides number of APIs, for C, C++ and scripting languages. Of course, it supports JPEG images and its variants like JPEG2000 and more.

Here is a very simple example how to open JPEG image and query its dimensions:

#include <gdal_priv.h>

GDALAllRegister(); // call ones in your application

GDALDataset* ds = (GDALDataset*)GDALOpen("my.jpeg", GA_ReadOnly);
int width  = ds->GetRasterXSize();
int height = ds->GetRasterYSize(),
int nbands = ds->GetRasterCount();

Check GDAL API tutorial for more complete example.

Get dimensions of JPEG in C++

6 Answers6