> What I am not familiar with is generating graphical plots, or even
> bitmap image files for that matter.
>
> Is there a recommended C/C++ plotting library which would be useful for
> generating a spectrogram (time vs. frequency with color-coded
> magnitude)?

I faced the same problems, by wanting to plot data into a bitmap, a couple 
of days ago, I googled and came across this library. I only handles the 
bitmap operations, but should be easily interfaced into some FFT/plot 
function.

http://easybmp.sourceforge.net/

--
Morten

BobM wrote:
> Hi Everyone,
>
> I'm looking to make a small C/C++ command-line utility which takes a
> binary audio file as input and generates a spectrogram of a given time
> range of the file.
>
> First off, I am already comfortable with reading/writing binary audio
> files, as well as the "back end" requirements for generating
> spectrogram information (FFT, windowing, etc.).
>
> What I am not familiar with is generating graphical plots, or even
> bitmap image files for that matter.
>
> Is there a recommended C/C++ plotting library which would be useful for
> generating a spectrogram (time vs. frequency with color-coded
> magnitude)?
>
> Adobe Audition works well for a one-off plot of a spectrogram, but I
> need to do this for hundreds of audio files. Thanks in advance for any
> help.

Hi Bob,

There are a couple of solutions that I can think of.

I've never used it this way, but I think there is a way to
send gnuplot the data from your program and have it
generate the plot. I'm not sure how you transfer the
data to be plotted to gnuplot, but I'm sure you can
google for it.

Another way, which really isn't a way since it doesn't
suit your requirement of a command-line program but
I thought I'd mention it anyway, is to develop a real
graphical application. It might not be as difficult
as you think if you based it on the fantastic wxwidgets
project. Google for more info.

--Randy



> 
> Regards,
> Bob

Hi Everyone,

I'm looking to make a small C/C++ command-line utility which takes a
binary audio file as input and generates a spectrogram of a given time
range of the file.

First off, I am already comfortable with reading/writing binary audio
files, as well as the "back end" requirements for generating
spectrogram information (FFT, windowing, etc.).

What I am not familiar with is generating graphical plots, or even
bitmap image files for that matter.

Is there a recommended C/C++ plotting library which would be useful for
generating a spectrogram (time vs. frequency with color-coded
magnitude)?

Adobe Audition works well for a one-off plot of a spectrogram, but I
need to do this for hundreds of audio files. Thanks in advance for any
help.

Regards,
Bob