Re: [Gimp-user] Is this compatible?

2006-10-09 Thread Chris Mohler

I stand corrected.

My PNG *does* match the original exactly, pixel per pixel.  I wasn't
hallucinating - just mistakenly opened the wrong two files for
comparison.

Chris.
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Re: [Gimp-user] Is this compatible?

2006-10-09 Thread Michael Schumacher
David Gowers wrote:

> Conclusion: monitor display artefact or your hallucination.

... or gamma correction? Unless you consider this an artefact.


HTH,
Michael

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Re: [Gimp-user] Is this compatible?

2006-10-08 Thread David Gowers
On 10/9/06, Chris Mohler <[EMAIL PROTECTED]> wrote:
When I open a file in GIMP, and save a copy as PNG, open the them upside-by-side: the colors habe been altered in the PNG (albeitslightly).  I consider that "loss", and I don't trust PNG for photos.
It would be loss if the colors had changed; however they haven't. I just checked by saving a PNG which had chosen colors in certain areas, then loading that PNG and comparing the color values to the original. No change. Conclusion: monitor display artefact or your hallucination.

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Re: [Gimp-user] Is this compatible?

2006-10-08 Thread Chris Mohler

When I open a file in GIMP, and save a copy as PNG, open the them up
side-by-side: the colors habe been altered in the PNG (albeit
slightly).  I consider that "loss", and I don't trust PNG for photos.
Web graphics - no problem.  PNG beats the hell out of GIF.  It just
isn't ready for pre-press yet, IMO.

Chris
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Re: [Gimp-user] Is this compatible?

2006-10-08 Thread Marco Wessel


On Oct 8, 2006, at 5:21 PM, Jozef Legeny wrote:



PNG supports indexed and grayscale color modes which aren't lossless,
however by default the PNG is entirely lossless


That is a bit of a weird definition of lossless. If you save an RGB32  
image as an indexed or grayscale PNG then yes, you've lost  
information. But that is inherent to grayscale and indexed images.  
You should have saved that as an RGB32 image, which PNG fully  
supports. In this case it isn't PNG throwing data away (like JPEG  
does), but the image editor (GIMP) converting to indexed/grayscale  
and then saving that. Indexed and grayscale modes in PNG are just as  
lossless as its non-indexed modes.


However like I said there are methods of tuning the PNG's compression  
to be lossy, and yet still be PNG-compatible. No image editors that I  
know of implement these methods, however. (http://membled.com/work/ 
apps/lossy_png/).


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Re: [Gimp-user] Is this compatible?

2006-10-08 Thread Jozef Legeny

On 10/7/06, Saul Goode <[EMAIL PROTECTED]> wrote:

> Mike Foster wrote:

> TIFF is another good option, however the Wikipedia entry for PNG says it
> uses a type of lossless compression.  Have I missed something here?  I
> am very curious to know the answer as I have started to save my
> completed photographs as PNG because I thought there was no penalty for
> doing so.

I agree with you, Mike. My understanding is that the different
compression settings of PNG only effect how rigorously (and time
consuming) the compression algorith is; i.e., that all PNG files are
losslessly compressed.



PNG supports indexed and grayscale color modes which aren't lossless,
however by default the PNG is entirely lossless

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Re: [Gimp-user] Is this compatible?

2006-10-07 Thread Saul Goode
> Mike Foster wrote:

> TIFF is another good option, however the Wikipedia entry for PNG says it 
> uses a type of lossless compression.  Have I missed something here?  I 
> am very curious to know the answer as I have started to save my 
> completed photographs as PNG because I thought there was no penalty for 
> doing so.

I agree with you, Mike. My understanding is that the different
compression settings of PNG only effect how rigorously (and time
consuming) the compression algorith is; i.e., that all PNG files are
losslessly compressed.


"It is amazing what you can accomplish if you do 
not care who gets the credit." -- Harry S. Truman

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Re: [Gimp-user] Is this compatible?

2006-10-07 Thread Michael Foster
TIFF is another good option, however the Wikipedia entry for PNG says it 
uses a type of lossless compression.  Have I missed something here?  I 
am very curious to know the answer as I have started to save my 
completed photographs as PNG because I thought there was no penalty for 
doing so.


Thanks,
Mike

http://en.wikipedia.org/wiki/PNG

Chris Mohler wrote:

My advice would be to save your files in TIFF format.  If you enable
LZW compression, the file size will be significantly reduced without
losing quality (unlike JPEG, and to some degree PNG).

I'm not sure what process your printer is using, but if it's just a
full-color transfer, a resolution of 200 DPI will be sufficient.

Chris



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Re: [Gimp-user] Is this compatible?

2006-10-07 Thread Marco Wessel


On Oct 7, 2006, at 7:25 PM, Chris Mohler wrote:


Apologies - forgot to "reply-all"

My advice would be to save your files in TIFF format.  If you enable
LZW compression, the file size will be significantly reduced without
losing quality (unlike JPEG, and to some degree PNG).


PNG is just as lossless as TIFF with LZW compression. There are ways  
of lossily compressing PNGs but they are non-standard and GIMP does  
not implement them as far as I know.


Either will suffice in this case as photoshop reads both, though its  
support for PNG in certain situations (mostly having to do with 16  
bits per channel images) is sub-par.



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Re: [Gimp-user] Is this compatible?

2006-10-07 Thread Chris Mohler

Apologies - forgot to "reply-all"

My advice would be to save your files in TIFF format.  If you enable
LZW compression, the file size will be significantly reduced without
losing quality (unlike JPEG, and to some degree PNG).

I'm not sure what process your printer is using, but if it's just a
full-color transfer, a resolution of 200 DPI will be sufficient.

Chris
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Re:[Gimp-user] Is this compatible?

2006-10-06 Thread Michael Foster

Anna Backstrom wrote:

I need to use a photo editor to edit some photos that will be put on
t-shirts.   The person that does the t-shirts uses Adobe Photoshop and I
was wondering if the edited photos from this program will be compatible
with Photoshop.

Thanks

Anna

  
You shouldn't have any problem, you'll just need to save the file in a 
different format as I don't think Photoshop can read GIMP's XCF files.  
If the Photoshop user plans to do more with the file once they get it, 
or if you plan to be exchanging it back and forth, then your best bet 
would be to save it as a PSD file.  If they are just taking your file 
and printing it directly then you could export it to PNG or JPG (if you 
need the file to be small).


Mike
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Re: [Gimp-user] Is this compatible?

2006-10-06 Thread Patrick Shanahan
* Anna Backstrom <[EMAIL PROTECTED]> [10-06-06 15:01]:
> I need to use a photo editor to edit some photos that will be put on
> t-shirts.  The person that does the t-shirts uses Adobe Photoshop and
> I was wondering if the edited photos from this program will be
> compatible with Photoshop.

I would think that there would be no problem as long as you save the
photos in a format that photoshop can read.
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[Gimp-user] Is this compatible?

2006-10-06 Thread Anna Backstrom
I need to use a photo editor to edit some photos that will be put on
t-shirts.   The person that does the t-shirts uses Adobe Photoshop and I
was wondering if the edited photos from this program will be compatible
with Photoshop.

Thanks

Anna
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