PDF Colo(u)r Analysis (without Acrobat itself ?)_问答_开发者

Is there a library/tool which would list all colours used in a PDF document ?

I'm sure Acrobat itself would do this but I would like an alternative (开发者_如何学Goideally something that could be scripted).

So the idea is if you have a very simple PDF document with four colours in it the output might say :

RGB(100,0,0)
RGB(105,0,0)
CMYK(0,0,0,1)
CMYK(1,1,1,1)

You could explore the insides with pdfbox, but you would have to write some code to find and catalog all those colors.

Most PDF tools have access to this information but no api to access it. You could take any tool and add it in

Apago PDFspy generates an XML file containing all kinds of metadata extracted from PDF files. It reports color usage including spot colors.

We recently added a function called GetPageColorSpaces(0) to the Quick PDF Library - www.quickpdflibrary.com to retrieve much of the ColorSpace info used in the document.

Here is some sample output.

Resource,\"QuickPDFCS2eb0f578\",Separation,\"HKS 52 E\",DeviceCMYK,0.95,0,0.55,0
Resource,\"QuickPDFCSb7b05308\",Separation,\"Black\",DeviceCMYK,0,0,0,1
Resource,\"QuickPDFCSd9f10810\",Separation,\"Pantone 117 C\",DeviceCMYK,0,0.18,1,0.15
Resource,\"QuickPDFCS9314518c\",Separation,\"All\",DeviceCMYK,0,1,0,0.5
Resource,\"QuickPDFCS333d463d\",Separation,\"noplate\",DeviceCMYK,1,0,0,0
Resource,\"QuickPDFCSb41cafc4\",Separation,\"noprint\",DeviceCMYK,0,1,0,0
Resource,\"Cs10\",DeviceN,Black,Colorant,-1,-1,-1,-1
Resource,\"Cs10\",DeviceN,P1495,Colorant,-1,-1,-1,-1
Resource,\"Cs10\",DeviceN,CalRGB,Colorant,-1,-1,-1,-1
Resource,\"Cs10\",Separation,\"P1495\",DeviceCMYK,0,0.31,0.69,0
XObject,\"R29\",Image,,DeviceRGB,-1,-1,-1,-1

Disclaimer: I work at Atalasoft.

Our product, DotImage with the PDF Reader add-on, can do this. The easiest way is to rasterize the page and then just use any of our image analysis tools to get the colors.

This example shows how to do it if you want to group similar colors -- the deployed example will only work for PNG and JPEG, but if you download the code, it's trivial to include the add-on and get PDF as well (let me know if you need help)

Source here:

http://www.atalasoft.com/cs/blogs/31appsin31days/archive/2008/05/30/color-scheme-generator.aspx

Run it here:

http://www.atalasoft.com/31apps/ColorSchemeGenerator

If you are working with specific and simple PDF documents from a constrained source then you may be able to find the colors by reading through the content stream. However this cannot be a generic solution.

For example PDF documents can contain gradients or transparency. If your document contains this type of construct then you are likely to end up with a wide range of colors rather than a specific set.

Similarly many PDF documents contain bitmapped images. Given that these will need to be interpolated to be displayed at different resolutions, the set of colors in a displayed PDF may be bigger or different to (though obviously broadly similar to) the embedded bitmap.

Similarly many PDF documents contain constructs in multiple color spaces that are rendered into different color spaces. For example a PDF might contain a DeviceRGB bitmap, a line in an ICC based CMYK color and a Lab based rectangle. The displayed version might be in sRGB for display or CMYK for print. Each of these will influence the precise set of colors.

So the only 100% valid answer is going to be related to a particular render of a PDF at a particular resolution to a particular color space. From the resultant bitmap you can determine the colors that have been used.

There are a variety of PDF libraries that will do this type of render including DotImage (referenced in another answer) and ABCpdf .NET (on which I work).