I found this graph that demonstrates the frequency response of a headphone of mine:

In fact it is part of a larger study that is on this page.
Now that I know the distortions of this headphone, could someone tell me how I can adjust the EQ accurately to compensate for these differences and create a completely flat response?

You could try this:
Try to Match the EQ curve with the Sonitus Equalizer like I did in the photo. I used the blue curve.
Then invert all the gain settings like this:
Set band 1 for -6.1 dB.
Set band 2 for +3.6 dB.
Set band 3 for -5.5 dB.
Set band 4 for -7.2 dB.
Set band 5 for +4.8 dB.
Set band 6 for -7.1 dB.
That should get you closer to flat. You will need to do some final adjusting by ear.
Note: You actual headphone may differ from the graph.  
 
 
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Also, look into SonarWorks. This is a program that does exactly what you are asking for.
The problem is that it does not support your particular headphone model: Philips SHB9100.
It does support the SHB9500.
You would have to purchase another headphone that is supported by the program.
 
https://www.sonarworks.com/reference
 

Thanks Mike. 
Could you tell me the difference between the blue line and the black line in the frequency response graph?

rogeriodec
Thanks Mike. 
Could you tell me the difference between the blue line and the black line in the frequency response graph?

The blue graph was obtained using a special stand (SF1) for the headphone and calibrated microphones.
It has a soft surface to reduce sound conduction and reflection. It has no "ears".
EDIT: See photo here: http://reference-audio-analyzer.pro/stands.php
 
The black graph was obtained using what  is known as a "Dummy Head" stereo microphone with ears (HDM1).
The headphone is placed on the "dummy head". The ears of the dummy head contain calibrated microphone elements.  
 
That said, perhaps you should try matching the EQ curve of the black curve. It may be a better approximation of
how the headphone actually sounds.
 
And remember... you are never going to get the headphones completely flat just by looking at a chart and trying to match and invert it.  But I am sure you can improve the sound of the headphone if you try.
The biggest improvement I can see would be to take some of the low frequency boost out.
The best way to learn is to do. Set up that EQ and start turning the knobs and learn what works and what doesn't work.
 
Put the Sonitus EQ in your master buss so that the entire mix is Equalized.
Bypass the EQ before you render a stereo mix. You don't want that EQ graph printed to your mix.
 
 
 
 
 
 
 

mikedocy
Also, look into SonarWorks. This is a program that does exactly what you are asking for.
The problem is that it does not support your particular headphone model: Philips SHB9100.
It does support the SHB9500.
You would have to purchase another headphone that is supported by the program.
 
https://www.sonarworks.com/reference
 

there is also the toonboosters offering, similar to sonarworks but has more headphones supported https://www.toneboosters.com/tb_morphit_v1.html

mikedocy
 

The blue graph was obtained using a special stand (SF1) for the headphone and calibrated microphones.
It has a soft surface to reduce sound conduction and reflection. It has no "ears".
EDIT: See photo here: http://reference-audio-analyzer.pro/stands.php
 
The black graph was obtained using what  is known as a "Dummy Head" stereo microphone with ears (HDM1).
The headphone is placed on the "dummy head". The ears of the dummy head contain calibrated microphone elements.  
 
That said, perhaps you should try matching the EQ curve of the black curve. It may be a better approximation of
how the headphone actually sounds.
 
And remember... you are never going to get the headphones completely flat just by looking at a chart and trying to match and invert it.  But I am sure you can improve the sound of the headphone if you try.
The biggest improvement I can see would be to take some of the low frequency boost out.
The best way to learn is to do. Set up that EQ and start turning the knobs and learn what works and what doesn't work.
 
Put the Sonitus EQ in your master buss so that the entire mix is Equalized.
Bypass the EQ before you render a stereo mix. You don't want that EQ graph printed to your mix.
 
 

Mike, the world would be a much better place if there were more people like you! 
Although the site is in Russian, thanks to the fabulous Google translator, it is possible to understand.
And we have to get the hat off for the work of these Russians.
I enjoyed the excitement and created a profile using FabFilter Pro-Q:

 
I used your technique of imitating the graph curve and then invert the frequencies, which in FabFilter is very simple.
 
Actually I went a little further by literally overlaying FabFilter over the original frequency response graph, leaving the plugin window semi-transparent (for that I used this Autohotkey script) and then resizing the window to exactly overlap the vertical and horizontal gridlines . Hence I basically drew the curves of the EQ over the black line of the graph.
The result was excellent. Fewer bass tones, and some variations in mid and treble.
Of course now I have to accustom my ears after so much time using this headphone without the proper calibration.
But now I think I'm on the right way. 

pwalpwal
 
there is also the toonboosters offering, similar to sonarworks but has more headphones supported https://www.toneboosters.com/tb_morphit_v1.html

Thanks for the tip!
They also has a profile for my headphone model.
I downloaded the demo version and tested it.
But interestingly, the frequency response of this plugin for my headphone is quite different from the eq I created based on the Russian graphic I showed at the beginning of this topic; mainly in the low frequencies where, instead of reducing them, as it should be, by inverting the excess frequencies emitted by the headphone, on the contrary, their profile increases these low frequencies even more!

The mid and high frequencies are somewhat similar to my EQ, but low frequencies are a serious problem.
Now I wonder, who's right? I bet on the Russians, which show all the variations and methods used for capturing, as shown by Mike in the previous post.

Interesting. I was thinking of getting morphit

toneboosters is a responsive dev, you should contact him directly if the results are unexpected... i should add that i use sonarworks because morphit wasn't around at that point