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80 lines
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3.2 KiB
Markdown
80 lines
No EOL
3.2 KiB
Markdown
---
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date: 2022-12-18 18:38:44-05:00
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draft: false
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math: false
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medium_enabled: true
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medium_post_id: 21f4d18fcb56
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tags: []
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title: Concatenating PDF files in Linux
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---
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Every so often I need to combine several images into a single PDF. First, to convert an image to a PDF we can use `imagemagick`.
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```bash
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convert -quality 100 Image.png Scanned.pdf
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```
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To combine or concatenate multiple PDF files, we can use `ghostscript`.
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```bash
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gs -sDEVICE=pdfwrite \
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-sOUTPUTFILE=output.pdf \
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-dNOPAUSE \
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-dBATCH \
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input0.pdf input1.pdf input2.pdf
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```
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| Flag | Description |
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| -------------- | ------------------------------------------------------------ |
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| `-sDEVICE` | Device used for processing the output file type. Use `pdfwrite` to write to a PDF file. |
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| `-sOUTPUTFILE` | Path to save the resulting file output. |
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| `-dNOPAUSE` | Disables the prompting and pausing at the end of each page. |
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| `-dBATCH` | Finishes interpreting after processing the inputted files |
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Alternatively you can use `pdftk`
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```bash
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pdftk input0.pdf input1.pdf input2.pdf \
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cat output output.pdf
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```
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Lastly, you can also use `imagemagick`. Do note, however, that this program often leads to larger file sizes.
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```bash
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convert input0.pdf input1.pdf input2.pdf output.pdf
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```
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## Aside: Pixel Densities
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One issue I came across is that the pages were of different sizes. This is often because the pages can be of different pixel densities.
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To check run `pdfimages` and look at the 3rd to last and 2nd to last columns:
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```bash
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pdfimages -list filename.pdf
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```
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```
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page num type width height color comp bpc enc interp object ID x-ppi y-ppi size ratio
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--------------------------------------------------------------------------------------------
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1 0 image 613 77 rgb 3 8 jpeg no 8 0 1071 1076 9456B 6.7%
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1 1 image 2692 3496 rgb 3 8 jpeg no 9 0 329 329 418K 1.5%
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2 2 image 613 77 rgb 3 8 jpeg no 8 0 915 919 9456B 6.7%
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2 3 image 2300 3016 rgb 3 8 jpeg no 15 0 282 282 322K 1.6%
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3 4 image 613 77 rgb 3 8 jpeg no 8 0 937 942 9456B 6.7%
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3 5 image 2356 3024 rgb 3 8 jpeg no 21 0 288 288 150K 0.7%
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4 6 image 1686 2200 rgb 3 8 jpeg no 27 0 204 204 622K 5.7%
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5 7 image 5100 7016 rgb 3 8 jpeg no 33 0 600 600 1193K 1.1%
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6 8 image 613 77 rgb 3 8 jpeg no 8 0 1104 1110 9456B 6.7%
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6 9 image 2776 3720 rgb 3 8 jpeg no 38 0 339 339 231K 0.8%
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7 10 image 613 77 rgb 3 8 jpeg no 8 0 939 943 9456B 6.7%
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7 11 image 2360 3072 rgb 3 8 jpeg no 44 0 289 289 151K 0.7%
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```
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We can then use `imagemagick` to enforce a certain pixel density. The tradeoff being that the file size might increase.
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```bash
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convert -density 300 input.pdf output.pdf
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```
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If you happen to know a different way to enforce a pixel density that doesn't have a file size increase tradeoff. Please get in touch. |