Thank you @cday
I want to prevent that by converting with the command ...
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./nconvert -brightness 124 -gamma 0.72 -dpi 300 -xall -out pdf -multi XnVOut.pdf M-PDF3-1.pdf
... the quality of my source document (whose properties are unknown) is degraded more than necessary.
How could the quality be degraded by converting?
I think, if the pictures in the document had 250 dpi and I convert it with the command "./nconvert -brightness 124 -gamma 0.72 -dpi 300 -xall -out pdf -multi XnVOut.pdf M-PDF3-1.pdf", then the quality will degrade because each conversion of dpi's will cause a light quality degradation.
The same applies to type of compression and amount of compression. When my source document has a different compression method than the target document then I have a loss of quality.
Perhaps this also applies to the "Depth" property?
cday wrote: ↑Wed Mar 31, 2021 6:09 pm
Given the way this now long thread has evolved, and the new insight provided above by Pierre into the 'DPI' value of a PDF file, I think it might be best if you review what you now need to know, and then post any questions that remain in a concise form...
Here are my questions:
Please note: I do not know anything about Ghostscript and it's role in converting or showing the properties of the pictures that are in the pdf.
Please note: In my source PDF's all included pictures will have the same properties. I will not have pictures with different properties in the same PDF.
Please note: All questions refer to pdf's that contain images.
1. My wish would be to just run the command ...
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./nconvert -brightness 124 -gamma 0.72 -xall -out pdf -multi XnVOut.pdf M-PDF3-1.pdf
... and all properties of the pictures in this pdf remains the same.
But in the meantime I know, this is not possible.
Question: Which of the following properties will be changed through the command above? And which of them will remain untouched? Are there even other picture properties, that will not be untouched through Nconvert and are not in the list below?
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Format : Portable Document Format
Name : pdf
Compression : Uncompressed
Width : 359
Height : 359
Components per pixel : 3
Bits per component : 8
Depth : 24
# colors : 16777216
Color model : RGB
Bytes Per Plane : 1077
Orientation : Top Left
Xdpi : 72
Ydpi : 72
Page(s) : 3
Info:
PhotometricInterpretation: 2
PlanarConfiguration: 1
SamplesPerPixel: 3
DateTime: 2021:04:01 09:14:49
Software: GPL Ghostscript 9.27
Metadata : ( EXIF ICC )
Color Profile : Artifex Software sRGB ICC Profile
(Until now I know it is at least the property xdpi and Ydpi and the property "compression", I guess also the property Depth.)
2. Question: Which of the following properties show me the real properties of the pictures that are in the pdf and which of them are fantasy values?
Code: Select all
Format : Portable Document Format
Name : pdf
Compression : Uncompressed
Width : 359
Height : 359
Components per pixel : 3
Bits per component : 8
Depth : 24
# colors : 16777216
Color model : RGB
Bytes Per Plane : 1077
Orientation : Top Left
Xdpi : 72
Ydpi : 72
Page(s) : 3
Info:
PhotometricInterpretation: 2
PlanarConfiguration: 1
SamplesPerPixel: 3
DateTime: 2021:04:01 09:14:49
Software: GPL Ghostscript 9.27
Metadata : ( EXIF ICC )
Color Profile : Artifex Software sRGB ICC Profile
(Until now I know it is at least the property xdpi and Ydpi and the property "compression", I guess also the property Depth.)
3. Question: I know, I can not get the real properties of the pictures that are in the pdf (In my pdf's all pictures will have the same properties. So no need to find out the properties of each picture separately).
Question: So how can I find out the real properties of my pictures that are in my pdf? Is there any third party tool, that can do this?
Thank you.