retrieve image information (height, width, dpi, color depth) from JPG, GIF, PNG: Java

retrieve image information (height, width, dpi, color depth) from JPG, GIF, PNG

Asked by: Ronald

I need to retrieve the "size" (in pixels and in inches/centimeters) and color depth from BMP, JPG, GIF and PNG files. The pixel size seems to be relatively easy, the dpi - value poses problems at least for PNG.

I would very much prefer a "pure JDK" solution (source level 1.6 is ok!) or a Sun library.
Some third party library must be small (< 100 KB), free and open source...

I'm quite good at Java, but the last time I used "Image"-objects was in Java 1.1 (!) :-) I hope some things have improved since then ;-)

Of course a "generic solution" for "almost any type of image" would be great. However, some special code for the above formats is also ok, I probably won't need more formats in the near future...

Thanks in advance for any help!

Instant Access to this Solution

Plus...

30 Day FREE access, no risk, no obligation

Collaborate with the world's top tech experts

Unlimited access to our exclusive solution database

Never be left without tech help again

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

"The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.

"Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin

"Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

ok, I solved it myself :-)

Just in case anybody else needs this: I'm now using the "Sixlegs PNG library" I mentioned above and I'll post an example below. The jar file is 29 KB and full source is provided. The one things I'm not absolutely sure about yet is the license. I'm not sure if I will ever publish my program but if I do, I don't think I want to publish the source code...

------ from the license -------------
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module. An independent module is a module which is not derived from
or based on this library. ...
------ from the license -------------

Sounds ok. I'm ok at English, but not so much at Legalese...

I now use two different libraries: One of PNG, one for BMP,GIF,JPG. That's ok, but not perfect. If anybody has a better solution, the points are still available :-)

So here we go with my code for PNG:

PngImage image = new PngImage();
image.read(file);
res.colorDepth = image.getBitDepth();
res.heightPx = image.getHeight();
res.widthPx = image.getWidth();
 
// in theory, the pixels don't have to be square pixels. I've never used that, but let's just calc x and y separately		
Integer dpmX = (Integer)image.getProperty(PngConstants.PIXELS_PER_UNIT_X); // dots per meter (!)
Integer dpmY = (Integer)image.getProperty(PngConstants.PIXELS_PER_UNIT_Y);
 
// being from Europe, I'm really a big fan of the metric system, but I've really never seen the "dots per meter" unit before ;-) I really don't know how much 23622 dots per meter is :-) So I'll stick with dpi just in this one case ;-)
if (dpmX != null) res.widthDpi = dpmX.intValue() * 254 / 10000;
if (dpmY != null) res.heightDpi = dpmX.intValue() * 254 / 10000;
// in theory, these are "dots per unit" and the unit *could* be something other than meter - does not seem to be used, though... at least not in my files
 
 
res.calcPageSize();
 
...
 
void calcPageSize() {
	if ((widthDpi > 0) && (heightDpi > 0)) {
		widthMM = widthPx * 254 / widthDpi / 10;
		heightMM = heightPx * 254 / heightDpi / 10;
		if ((widthMM > 195) && (widthMM < 220) && (heightMM > 280) && (heightMM < 310)) {
			this.pageFormat = ImageInfo.PageFormat.DIN_A4; // enum
		}
		else { // several other formats.... }
	}
	else ...; // do some guessing based on aspect ratio...
}
 
//This  is not *exactly* how it appears in my code, but I hope everybody sees what it does...

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:

Select all Open in new window

Question

retrieve image information (height, width, dpi, color depth) from JPG, GIF, PNG

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

Java

Multimedia Programming with Java

Java Programming Language

Java Standard Edition

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Need individual assistance?

Our experts are ready to help.

Want to learn from the best?

Read articles from industry experts.

Working on a long term project?

Store your work and research.

What Makes Experts Exchange Unique?

Trusted by the world's most respected brands.

Faithfully serving IT professionals since 1996.

Related Solutions

Free Tech Articles

Cloud Class Webinars

Join the Community

Give a Little. Get a Lot.

Answers

3 Ways to Join

The Experts

The Experts

Testimonials

Testimonials

Testimonials

Business Clients

Business Clients

In the Press

In the Press

In the Press