I need to extract vector graphics from a PDF image and import them into GIMP, either as paths or as high-resolution raster images. Specifically, I need to get contour lines from USGS topographical maps and overlay them on satellite images. Any suggestions?
So far I have tried:
--Using GIMP's native PDF importing function to import them as raster images. Problem: To do so at high resolution crashes my computer. Possible solution would be to import only a selected area of a PDF, but as far as I can tell this is not possible.
--Using ImageMagick to convert the PDF to a raster image. Problem: Used with the "-scale" parameter, "convert" appears to rasterize the PDF and then upscale it, leading to a choppy image.
--Using InkScape to extract the necessary vector elements from the PDF. Problem: InkScape freezes when I try to open a moderately large (25 Mb) PDF.
Any other ideas?
Many thanks,
treacl
The option you didn't mention above is to try to use the ghostscript program directly to render your output - ghostscript is used internally by GIMP to import PDF files, so you likely have it installed already.
There are tens of command switches to pass ghostscript for it to render a file into another format - the switches you need to pass are for determining the output size, resolution and which page to print. I didn't find any switch to select a portion of the page to be rendered - so, if your document is a single page, it is possible the generated file will still be to big for GIMP - but you will likely be able to crop it with ImageMagick, at least.
I guess the relevant command line for you would be something along:
gs -dNOPAUSE -dBATCH -sDEVICE=png16m -sOutputFile=page.png -dFirstPage=<pagenumber> -dLastPage=<pagenumber> -r<dpiresolution> -f<filename.pdf>
If the resulting image is still too large to be generated or operated upon, you can try changing the output format to use a smaller color depth (this one is 3 bytes per pixel: png16m) . It should be possible to pass postscript commands to transform the device, so that the area of interest is scaled up to your page size (and the remaining parts are cropped out of the rendering) - that would be the definitive fix for you - but of the top of my head, I don't know how to do that with ghostscript.
Alternatively, you can try passing ImageMagick the -density parameter as suggested in the comments.
Related
I am getting a BMP from a PDF with GhostScript, but its content is not fitted into page boundaries. Even I try any option, I am not able to get the content fitted.
I've tried to generate the BMP with different GhostScript options, but noone seems to fit 100% ok the content.
This is the last command I tried. Please, don't expect it to have what I need, just copied & paste from tty.
gs -dBATCH -dNOPAUSE -sPAPERSIZE=a4 -dFIXEDMEDIA -dPSFitPage -sDEVICE=bmpmono -sOutputFile=Betlem.bmp -g1184x968 -c "<</PageSize [900 500]>> setpagedevice 0 0 translate" -c "<</PageOffset [-23 -100]>> setpagedevice" -f Betlem.pdf
I am expecting to get the content fitted into the BMP image borders, without exception of a pixel. I am using an OpenCV & Python function to extract content and fit in new image and this is the debug:
initial BMP image resolution = (872, 900)
BMP image resolution after fit content into new page = (541, 870)
Have a look to the following thread for the fitting funtion in Python:
I can't find a way to fit contour on new image zero point
You are using PSFitPage for a PDF file, you should be using PDFFitPage or just FitPage.
Note that the 'fitting' in this case is fitting the PDF media size to the existing media. If the PDF content leaves white space around the edge of the media, then the resulting scaling will include that.
In addition you are using PostScript to offset the page origin, which will introduce white space, and you are trying to change the media size, which won't work because you've set -dFIXEDMEDIA. Using these in combination with any of the FitPage switches is not likely to work well.
Randomly stabbing at controls and copying bits of code intended to solve different problems isn't likely to help you I'm afraid.
Without seeing an example file I can't, of course, tell you how to solve your problem, and I'm not really sure exactly what you are trying to achieve. A bitmap with no white space ? A bitmap of a given size with no white space ? Something else ?
[Edit]
OK so looking at the PDF file, the media box is 11.69x8.27 inches, there is white space at the top, bottom, left and right between the marks on the page and the edge of the media.
Running this through Ghostscript, to TIFF at 72 dpi results in a file which Adobe Photoshop says is 11.694x8.264 inches and has white space at top bottom left and right, just like the PDF file.
By default Ghostscript uses the Media size from the PDF to render to, however you can change this. If you were to change the media size to (say) 5.8x4.14 inches, set -dFIXEDMEDIA and then rendered the PDF file what would happen is that the top and right hand side of the PDF file would be 'off the page' so you would only get the left hand portion rendered. Try this:
gs -DEVICEWIDTHPOINTS=421 -dDEVICEHEIGHTPOINTS=298 -dFIXEDMEDIA "A betlem m en vull anar(1).pdf"
You will see the white space is still present at bottom and left, and the top and right have fallen off the page.
Now, if you add FitPage that will scale the original media down until it fits the new media size (and all the content too, of course). If you try:
gs -DEVICEWIDTHPOINTS=421 -dDEVICEHEIGHTPOINTS=298 -dFIXEDMEDIA -dFitPage "A betlem m en vull anar(1).pdf"
You'll see that the output is the same physical dfimensions as the previous command, but now the whole of the PDF content can be seen because its been scaled down. You should also see that the distribution of white space has changed, because I didn't strictly divide by 2 in each direction. The FitPage switch scaled the content in both directions by the same amount, and distributed the extra space in the x direction evenly to each side, as new white space.
Now I've no clue what you mean by 'simmetric'. You can undoubtedly do what you want using Ghostscript and the PostScript language, but I don't know what it is you want. Pointing me at Python code isn't going to help I'm afraid, I don't speak Python.
I can say that Ghostscript does not add extra white space that isn't present in the original unless you mess with the rendering by addding parameters like FitPage and FIXEDMEDIA.
If you can explain what you are trying to achieve I can probably tell you what to do.
I have an image of a website which I'm trying to convert to PDF. I have the image in several formats: PSD, PNG, JPG, TIFF, all saved losslessly.
I'm using the following command to convert the image to PDF:
convert -density 93 foo.jpg bar.pdf
Here is part of the original image:
And here is the same part, after converting to PDF:
As you can see, the second one is ever so slightly hazy. What's causing this, and how can I eliminate it? I've seen PDFs with crisp graphics, so I know it's possible.
If you are seeing the same results with multiple input types. The fuzziness is likely being caused by the anti-aliasing feature of your PDF Viewer. If using Acrobat, you can turn off image anti-aliasing by doing the following:
Go to Edit-->Preferences-->Page Display
Untick the option "Smooth Images" and hit "OK".
The crisp graphics you are seeing on other PDFs are likely due to the fact that they are vectorized graphics. Imagemagick is creating a PDF and embedding your image inside of it which may be subject to compression.
Also:
When using jpeg as input, add the "-quality 100" to your Imagemagick call to retain the highest quality possible.
Use a higher value for the "-density" parameter (I would recommend at least 150) to generate a higher resolution PDF.
I have a very specific requirement where i must automatically stamp every page of a PDF file (for a faxing application), so here's the process i've made:
step 1: Convert PDF to PNG, one png file per page
cmd1: gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -dGraphicsAlphaBits=4 -dTextAlphaBits=4 -r400 -sOutputFile=image_raw.png input.pdf
cmd2: mogrify -resize 31.245% image_raw.png
input.pdf (input): https://www.dropbox.com/s/p2ajqxe99nc0h8m/input.pdf
image_raw.png (output): https://www.dropbox.com/s/4cni4w7mqnmr0t7/image_raw.png
step 2: Stamp every PNG file (using a third party tool ..)
image_stamped.png (output): https://www.dropbox.com/s/3ryiu1m9ndmqik6/image_stamped.png
step 3: Reconvert PNG files into one PDF file
cmd: convert -resize 1240x1753 -units PixelsPerInch -density 150x150 image_stamped.png output.pdf
output.pdf (output): https://www.dropbox.com/s/o9y0jp9b4pm08ci/output.pdf
The output file of the third step shal be "theoretically" the same as the input file in step 1 (plus the stamp on it) but it's not, the file is somehow blurry and it turns to be unreadeable for humans after faxing it since blurred pixels wouldnt pass through fax wires even if you may see no difference between input.pdf and output.pdf, try zooming in and you'll find that text characters are blurred on its edges.
What is the best parameters to play with at input (step 1) or output (step 3) ?
Thanks !
You are using anti-aliasing (TextAlphaBits=4). This 'smooths' the edges of text by introducing grey pixels between the black pixels of the text edges. At low resolutions (such as displays) this prevents the 'jaggies' in text and gives a more readable result. At higher resolutions its value is highly debatable.
Fax is a 1-bit monochrome medium, so the grayscale values have to be recreated by dithering. As you have discovered, this is not a good idea in a limited resolution device as it leads to a loss of sharpness.
I believe that if you remove the -dTextAlphaBits=4 you will see an immediate improvement. I would also suggest that you remove the GraphicsAlphaBits as well, since this will have the same effect on linework.
If you believe that you still want anti-aliasing you could try reducing the aggressiveness, you currnetly have it set to 4, try reducing it to 2.
Regarding the other comments;
Kurt is quite correct, as is fourat, and I'm afraid MarcB is mistaken, the -r400 sets the resolution for rendering, in dots per inch. If only one number is given it is used for both x and y resolution. It is possible to produce a fixed size raster using Ghostscript, but you use the -dFIXEDMEDIA with -sPAPERSIZE switches or the -g switch which also sets FIXEDMEDIA automatically.
While I do agree with yms and Kurt that converting the PDF to a bitmap format (PNG) and then back to PDF will result in a loss of quality, if the final PDF is only used for transmission via fax, it doesn't matter. The PDF must be rendered to a fax-resolution bitmap at some point in the process, its not a big problem if its done before the stamp is applied.
I don't agree with BitBank here, converting a vector representation to bitmap means rasterising it at a particular resolution. Once this is done, the resulting image cannot be rescaled without loss of quality, whereas the original vector representation can be as it is simply rendered again at a different resolution. Image in PDF refers to a bitmap, you can't have a vector bitmap. The image posted by yms clearly shows the effect of rendering a vector representation into an image.
One last caveat. I'm not familiar with the other tools being used here, but two of the command lines at least imply 'resize'. If you 'resize' a bitmap then the chances are that the tool will introduce the same kinds of artefacts (anti-aliasing) that you are having a problem with. Onceyou have created the bitmap you should not alter it at all. Its important that you create the PNG at the correct size in the first place.
And finally.....
I just checked your original PDF file and I see that the content of the page is already an image. Not only that its a DCT (JPEG) image. JPEG is a really poor choice of format for a monochrome image. Its a lossy compression format and always introduces artefacts into the image. If you open your original PDF file in Acrobat (or similar viewer) and zoom in, you can see that there are faint 'halos' around the text, you will also see that the text is already blurry.
You then render the image, quite probably at a different resolution to the original image resolution, and at the same time introduce more blurring by setting -dGraphicsAlphaBits. You then make further changes to the image data which I can't comment on. In the end you render the image again, to a monochrome bitmap. The dithering required to represent the grey pixels leads to your text being unreadable.
Here are some ways to improve this:
1) Don't convert text into images like this, it instantly leads to a quality loss.
2) Don't compress monochrome images using JPEG
3) If you are going to work with images, don't keep converting them back and forth, work with the original until you are done, then make a PDF file from that, if you really must.
4) If you really insist on doing all this, don't compound the problem by using more anti-aliasing. Remove the -dGraphicsAlphaBits from the command line. You might as well remove -dTextAlphaBits as well since your files contain no text. Please read the documentation before using switches and understand what it is you are doing.
You should really think about your workflow here. Obviously we don't know what you are doing or why, so there may well be good reasons why some things are not possible, but you should try and avoid manipulating images like this. Because these are not vector, every time you make a change to the image data you are potentially losing information which cannot be recovered at a later stage. By making many such transformations (and your workflow as depicted seems to perform as many as 5 transformations from the 'original' image data) you will unavoidably lose quality.
If possible retain everything as vector data. When it is unavoidable to move to image data, create the image data as you need it to be finally used, do not transform it further.
I've had a closer look at the files you provided, see here:
So, already the first image (image_raw), the result of the mogrify resize command, is fairly blurry at 1062x1375. While the blurriness does not get worse in the second image (image_stamped) which is the result of the third-party tool, the third image (extracted from your output.pdf), i.e. the result of that convert command, is even more blurred which is due to the graphic being resized (which is something you explicitly tell it to do).
I don't know at which resolution your fax program works, but there is more quality loss still, at least due to 24 bit colors to black-and-white transformation.
If you insist on the work flow (i.e. pdf->png->stamped png->pdf->fax) you should
in the initial rasterization already use the per-inch resolution your rastered image will have in all following steps (including fax transmission),
refrain from anti-aliasing and use of alpha bits (cf. KenS' answer), and
restrict the rasterized image to the colorspace available to the fax transmission, i.e. most likely black-and-white.
PS As KenS pointed out, already the original PDF is merely a container for an image (with some blur to start with). Therefore, an alternative way to improve your workflow is to extract that image instead of rendering it, to stamp that original image and only resize it (again without anti-aliasing) when faxing.
I've been using Ghostscript to convert my single figure plots rendered in PDF to PNG:
gswin32c -sDEVICE=png16m -r300x300 -sOutputFile=junk.png ^
-dBATCH -dNOPAUSE Figure_001-a.pdf
This works in the sense I get a PNG out and it contains the plot.
But it contains a huge amount of white space as well (an example source image: http://cdsweb.cern.ch/record/1258681/files/Figure_001-a.pdf).
If you view it in Acrobat you'll note there is no white space around the plot. If you use the above command line you'll find the plot is only about 1/3 of the space.
When doing the same thing with an EPS file I run into the same problem. However, there is the command-line parameter -dEPSCrop that one can pass to get the PS rendering engine to pay attention to the BoundingBox.
I need the similar argument for rendering PDFs. I was not able to find it in docs (nor even the -dEPSCrop, actually).
I had exactly the same issue. I fixed it by adding -dUseArtBox switch.
Example:
/usr/bin/gs -dUseArtBox -dNOPAUSE -sDEVICE=pngalpha -sOutputFile=output.png input.pdf
Note: -dUseArtBox switch is supported since ghostscript version 9.07
-dUseArtBox
Sets the page size to the ArtBox rather than the MediaBox. The art box defines the extent of the page's meaningful content (including potential white space) as intended by the page's creator. The art box is likely to be the smallest box. It can be useful when one wants to crop the page as much as possible without losing the content.
There are various options to control which "media size" Ghostscript renders a given input:
-dPDFFitPage
-dUseTrimBox
-dUseCropBox
With PDFFitPage Ghostscript will render to the current page device size (usually the default page size).
With UseTrimBox it will use the TrimBox (and it will at the same time set the PageSize to that value).
With UseCropBox it will use the CropBox (and it will at the same time set the PageSize to that value).
By default (give no parameter), Ghostscript will render using the MediaBox.
For your example, it looks like adding "-dUseCropBox" will do the job you're expecting.
Note, you can additionally control the overall size of your output by using "-sPAPERSIZE" (select amongst all pre-defined values Ghostscript knows) or (for more flexibility) use "-dDEVICEWIDTHPOINTS=NNN -dDEVICEHEIGHTPOINTS=NNN".
Have you tried using pdfcrop using pdftex (comes with texlive for example) or (not tried yet) the python script pdfcrop?
I have a similar workflow using the first tool mentioned.
I generate a figure in MATLAB with large amount of elements (100000+) and want to save it into a PDF file. With zbuffer or painters renderer I've got very large and slowly opened file (over 4 Mb) - all points are in vector format. Using OpenGL renderer rasterize the figure in PDF, ok for the plot, but not good for text labels. The file size is about 150 Kb.
Try this simplified code, for example:
x=linspace(1,10,100000);
y=sin(x)+randn(size(x));
plot(x,y,'.')
set(gcf,'Renderer','zbuffer')
print -dpdf -r300 testpdf_zb
set(gcf,'Renderer','painters')
print -dpdf -r300 testpdf_pa
set(gcf,'Renderer','opengl')
print -dpdf -r300 testpdf_op
The actual figure is much more complex with several axes and different types of plots.
Is there a way to rasterize the figure, but keep text labels as vectors?
Another problem with OpenGL is that is does not work in terminal mode (-nosplash -nodesktop -nodisplay) under Mac OSX. Looks like OpenGL is not supported. I have to use terminal mode for automation. The MATLAB version I run is 2007b. Mac OSX server 10.4.
This is a funny one. Your problem is not Matlab, it's Ghostscript (Matlab creates PDFs by calling Ghostscript, at least on Windows). When I run
x=linspace(1,10,100000);
y=sin(x)+randn(size(x));
plot(x,y,'.')
print -dpsc2 test.ps
I've got a 2Mb PS file (all vector, of course), which when compressed became a 164Kb ZIP. One would expect to get more-or-less the same result when converting PS to PDF, but ps2pdf test.ps produced your 4Mb file!
Since you are on a Mac, you probably have Distiller. I'd give it a try — generate PS files as above, and then run them through Distiller; you should get a 150K vector PDF.
If you insist on rasterizing, I can suggest printing the figure without any axes or labels to a tiff, opening the tiff, and recreating axes and labels on top of it.
If you don't want to go with a 2D histogram (i.e. an image where pixel brightness corresponds to density of points) as BlessedKey suggests, it looks like the only good way is to do the rasterizing yourself, as mentioned by AB.
getframe followed by frame2im seems to be the way to go for that. Unfortunately, getframe returns empty if you run with -nodisplay. Therefore, you'd have to save the figure as .fig, and on another computer run a script that
opens the figure, gets the content of the axes with getframe, displays the image from getframe and then saves to pdf.
As an alternative to simple plotting or a 2D histogram, you may want to look into scattercloud, which combines plotting the points with density information, by the way.
If at all possible you should try to subsample your problem before building the illustration. If you are plotting points on a curve then 10,000 is probably more than you need. A modern printer is only about 600 DPI afterall.
If the points are illustrating a cloud with some density properties, a better solution may be to build a two dimensional histogram first, and illustrate that with imshow or imagesc.
If multiple clouds are being illustrated with different colors you may be interested in building one such image for each cloud and the combining them with transparency.