Editing TIFF Headers

[tad]

OK,,,so no one is interested in color profiles,,,BUT, perhaps someone out there knows how to edit a .tif header in wordpad(?) so I can get RID of a color profile....Anyone ???.....Thanks,,,,Tad

[Sean Sedwards]

What is the source of your image and why do you want to remove the profile? TIFF files are modular and can be broken up, however they are binary files, not text, and may also be compressed. Removing any part is likely to be way beyond Wordpad.

By 'colour profiles' I presume you mean what PhotoShop calls printer profiles, which are tables of values that PhotoShop can use as an alternative to its normal CMYK separation settings. Although possible, AFAIK the table is not embedded in the TIFF, it's just used to create the separations for a specific printer. As I've said before, CMYK is an output format - a convenient way of grouping four colour corrected plates - and is usually only reversible by clicking undo just after creating it. Once you've reduced the colour gamut to fit a printing process, the original information is lost.

I think I need more information before I can give you a useful answer :-)

Regards - Sean

[tad]

Hi Sean,
Well, the issue is that Photoshop5 people are going to be giving us Xara users bitmap files with embedded ICC color profiles, eg. Kodak's ProPhoto colorspace. This happens EVERY TIME a file is OPENED in Photoshop.(File>ColorSettings>RGB Setup)
So this means that if we open (import) it into another colorspace EVERY PIXEL WILL BE CHANGED...I suspect that *CorelXara* ignores any embedded profile, but wonder about XaraX..Admittedly, every program has a *colorspace*, whether we know it or not, but I am forseeing a lot of nightmare situations, and would like to be able to off an embedded profile, although I fear that too would change every pixel..I've been checking the *Applied Color Theory* forum, and the questions have appeared, but no answers..I thought that those of you who write code might be able to look into the TIFF file and *see* what they are up to.
(*up to*! hey, I learned English in the USA)
Regards.......Tad [img]/infopop/emoticons/icon_biggrin.gif[/img]

[This message was edited by Tad Bridenthal on August 17, 2000 at 10:59 AM.]

[This message was edited by Tad Bridenthal on August 17, 2000 at 11:01 AM.]

[Sean Sedwards]

I have access to PhotoShop 4 but I don't use it myself because I dislike the way it mangles the image in apparently unpredictable ways - it's not just how the image appears on screen, the data is actually altered. For routine pixel twiddling I prefer the simplicity and predictability of Paint Shop Pro and I'd choose Satori for 'painting', although I don't do much of that.

I stand by what I said about CMYK TIFFs, however RGB may be a different story. I'd be interested to investigate further, so perhaps you could e-mail me a small RGB TIFF created in Xara and the same thing opened and exported as an RGB TIFF in PhotoShop.

Regards - Sean

[Sean Sedwards]

Tad

I've had a look at the two TIFFs you sent me off-conference and the good news is that the actual bitmap data is identical. There is some monitor calibration information embedded in the PS TIFF, but it seems to be in a PhotoShop specific format, unlikely to be read by any other program now or in the future. Although TIFF and PNG support the inclusion of colour space information as standard, I haven't come across an app. that actually uses the facility.

Regards - Sean

[tad]

Good work Sean !
I'm attaching a (reduced) combo image so you can see just HOW different those two were/are.
BTW, did you use something like the Norton Hex editor to check out the images ??
Many Thanks,,,,,,Tad
[img]/infopop/emoticons/icon_biggrin.gif[/img]

[Sean Sedwards]

I'd worry that if I hadn't bothered to calibrate my monitor or had done it incorrectly, PhotoShop would be embedding bogus information which might be wrongly interpreted by a print bureau, say. I prefer the KISS approach - Keep It Simple, Stupid!

To check that the images were identical, I compared them in Paint Shop Pro, which definitely doesn't support monitor calibration. I then viewed the files in Wordpad to see their general layout and read any embedded text. With experience it's possible to pick out header information (not necessarily at the beginning of the file) from image / preview data and to spot if compression has been used. Finally, I used MS Debug (a simple hex editor dating from the early days of DOS ) to obtain the precise information.

Regards - Sean