my dpx file are darker once converted

[miqui0287]

Hi all!

I have been using the Api ImageMagick++ on Visual Studio 2010 and it works perfectly.
But I'm in trouble with DPX files. Indeed, I load DPX images thank the read method of the Image Class and save them thank the write method like following :

Code: Select all

#include <Magick++.h>
#include <string>
#include <iostream>


using namespace std;
using namespace Magick;

int main( int /*argc*/, char ** argv)
{
  
  // Initialize ImageMagick install location for Windows
  InitializeMagick(*argv);
  Image my_image;
  my_image.read("a.dpx");

  my_image.write("./out/b.tiff");
  my_image.write("./out/c.dpx");
  my_image.write("./out/d.bmp");
  my_image.write("./out/e.jpg");

  return 0;
}

The files are well saved, good height, good width, goop depth, ... but when I look them in IMDisplay, for example, only the "c.dpx" image looks like "a.dpx". The others are similary but really darker.

Where does come from this darkness and is there a solution to my problem ?

Thx for your replies.

M.

[snibgo]

Do you get the same dark results from the command line:

Code: Select all

convert a.dpx b.tiff

If so, it may be a RGB/sRGB issue. What version IM are you running? Can you post a.dpx somewhere?

[miqui0287]

Hi Snibgo !

Thx for you reply.
Try to use convert.exe was a good idea but unfortunatly it did the same...

I'm working with the ImageMagick-6.8.1-Q16_vs2010 version and my aim is to use Magick++ Classes in my own code.

I'm going to try to change color space (sRGB->RGB), before save my new image in tiff.

I could post my dpx image somewhere, it's a 4K 16bits file, so you guess it's a heavy file (50 Mo, 30 when I zip it).
May be, I could send it to you by personal message or you could give a space where I would post it.

Thx.

M.

[snibgo]

dropbox.com is a common place for this. A zip is best, or the server might try to convert it to a jpeg or something, possibly using ImageMagick, and that confuses every one.

[miqui0287]

Here is my dpx file :

http://dl.dropbox.com/u/27496908/a.zip

Thank for your help !

[miqui0287]

I'm now trying to change the colorspace of my Image, but I fail...

I tried this :

Code: Select all

	Image my_image;
	my_image.read("a.dpx");
        my_image.colorSpace(Magick::RGBColorspace);
        my_image.write("./out/c.dpx");
        my_image.write("./out/b.tiff");

c.dpx is exactly the same as a.dpx, but b.tiff is completly black.

I tried also :

Code: Select all

	Image my_image;
	my_image.read("a.dpx");
        my_image.type(TrueColorType);
        my_image.write("./out/c.dpx");
        my_image.write("./out/b.tiff");

And I get exactly the same problem...

I hope, you'll be luckier!

M.

[snibgo]

Yeah, it's dark, isn't it?!

But not entirely black. "identify -verbose" says the pixels have a mean of about 0.02 (on a scale of 0 to 1). Doing a simple conversion to tiff gives the same mean pixel values, although "identify" says the dpx is RGB and the tiff is sRGB.

We can force a conversion, after declaring the dpx to be in RGB:

Code: Select all

convert a.dpx -set colorspace RGB colorspace sRGB a1.tiff

Now "identify" says the mean values are about 0.15, and I can see leaves against a dark background, with a hazy light bottom-centre.

(Instead of "-set colorspace RGB colorspace sRGB", I could use "-gamma 2.2" to give almost the same result.)

I can easily get a more visible image ...

Code: Select all

convert a1.tiff -auto-level -auto-gamma a2.tiff

... so if you just want to view the image, this works fine.

I have no viewers for dpx files, and don't know what the image should look like. Does "-set colorspace RGB colorspace sRGB" give you the result you expect?

(I've converted to tiff because that's what I generally use, but converting to jpg gives the same results.)

[miqui0287]

Hum...it seems that "convert a.dpx -set colorspace RGB colorspace sRGB a1.tiff" doesn't run on my computer, but "convert a.dpx -colorspace RGB a1.tiff" does.

The result of this command line is the same as former result...but when I try this "convert a.dpx -colorspace sRGB a1.tiff", I get what I was expecting !!!

You were right, it was colorspace problem...

I added just one 's' to my code :

Code: Select all

       Image my_image;
       my_image.read("a.dpx");
            my_image.colorSpace(Magick::sRGBColorspace);
            my_image.write("./out/b.tiff");

And I get my result!

Thank you for your help!

BTW, if you want to watch DPX file, use IMDisplay. Its exe file is the same directory of convert.exe, identify.exe,...

Bye

M.

[snibgo]

Bother, sorry, it needs another "-" before "colorspace:

Code: Select all

convert a.dpx -set colorspace RGB -colorspace sRGB a1.tiff

Sadly, imdisplay doesn't work under Windows, which is what I have in front of me. Besides, using IM software to verify other IM software would be dodgy.

But you've got it working, so that's good.

[miqui0287]

I'm working on Window seven and IMDisplay works perfectly.

Moreover, it seems it had been developped with MFC so it should work on window.

It's a shame, you can't use it, because it's a powerful tool.

See you.

M.

[snibgo]

Ah, yes ... imdisplay won't start for me from the command line, but does from start, all programs, etc. The recent-files list shows that I have used it before. I need to remember that I have it.