[magick-users] imagemagick convert PDF to JPG/PNG

[Avi Kouzi]

here (both ACDSEE and Firefox) shows the PNG file with the same result 
as the JPEG does (with edge artifacts).

Using the RGB version of the PDF - there are still slight color 
diffrences but not as much as with the CMYK version.
Question: why wouldn't the CMYK version work correctly in the first 
place using the -colorspace and such? (just like converting the CMYK to 
RGB in acrobat, or any other photo editing software for that matter?)

In regards to what you say about the DCT encoding, is it correct for me 
to assume I should be using PNG instead of JPEG?
And is there no way to tell imagemagick do the same trick photoshop 
does? (wrapping the DCT encoding inside the JPEG instead of rasterizing 
and re-encoding?)

I just need it to work correctly, does not really matter if the source 
file is CMYK or RGB and if the output file is JPEG or PNG.
Perhaps a different software can help resolve this issue? maybe 
converting the PDF to some middle-man format that will convert to JPEG 
or PNG?

I appreciate the help,
Avi.

Ross Presser wrote:
> The edge noise appears to me to be standard JPEG artifacting. If your
> original PDF stored the image using DCT encoding within the PDF, then
> the conversion process from PDF to bitmap back to JPEG is unavoidably
> going to add more artifacting, because of JPEG being a lossy format.
> It seems likely that this doesn't happen when you use Photoshop as the
> intermediary because Photoshop might be pulling the actual DCT encoded
> data from the PDF and wrapping it in the JPEG file format -- rather
> than rasterizing and re-encoding, as ImageMagick must do, since it
> doesn't itself know about the PDF file format but relies on a
> delegate.
>
> I don't see any way to completely eliminate this and still have a JPEG
> final output.
>
> The PNG you posted doesn't show edge artifacts that I can see. It has
> markedly different colors but that is because it started from the CMYK
> pdf.  Are the colors right if you start from the RGB pdf? If they are
> not, then the solution would be to have Ghostscript (the PDF delegate)
> use the right ICC profile that matches what is in the PDF.
>
> On 4/9/08, Avi Kouzi <avi at phpclub.org> wrote:
>   
>> I already tried the first one, it gives out pretty much the same results
>> as converted.jpg, the second one wouldn't run since I don't have those
>> ICM/ICC files (nowhere to be found on my filesystem).
>>
>> Also, now that I have the RGB PDF, it is still not helping much (as
>> there is still a slight color diffrence and the edges issue).
>>
>> duc.sequere.aut.de.via.decede at imagemagick.org wrote:
>>     
>>>> It seems that the PDF was in CMYK
>>>>
>>>>         
>>> Did you try
>>>
>>>   convert -colorspace rgb image.pdf image.jpg
>>>
>>> or
>>>
>>>   convert image.pdf -profile USWebCoatedSWOP.icc -profile sRGB.icm
>>>       
>> image.jpg
>>     
>>> Both methods are the suitable for properly converting a CMYK PDF to RGB
>>>       
>> JPEG.
>>     
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