Show HN: Make PDFs look scanned (CLI or in the browser via WASM)
github.com96 points by overflowy 9 hours ago
96 points by overflowy 9 hours ago
I made this because the online "make my PDF look scanned" tools want you to upload your file to their servers, which feels sketchy at best. Also, I wasn't happy with the output they produce, I wanted something that looks realistic.
I'm having a similar use case from time to time, I just use imagemagick magick -density 150 input.pdf \
-colorspace Gray \
-virtual-pixel White -background White \
-rotate 0.7 +repage \
-attenuate 0.45 +noise Gaussian \
-blur 0x0.4 \
-brightness-contrast -5x12 \
-compress jpeg -quality 78 scanned.pdf I have something similar. Someone asked for a signed PDF. I digitally signed it and sent it to them. They said it has to be scanned. So I did some image magic fu to it to rotate it and make it look crappy. Then they accepted it. My goto technique: apply signature stamp. Flatten. Change blend mode to multiply. Convert page to image. Rotate image by 0.5 deg. Paste scanned page on tape. Flatten. Change blend mode of image to burn or multiply. Convert to image. The only tell tale sign is that the text still has this aliasing like texture that doesn’t happen in real scanned pages. Yeah I don't want to rain on OPs parade; but this is already a solved problem: From my bookmarks (found on HN originally!) https://gist.github.com/andyrbell/25c8632e15d17c83a54602f6ac... I just display the PDF on my monitor and use my phone to take a photo of it. Scanner apps are good at eliminating moire patterns while accentuating the dust on my monitor. It looks highly realistic. It's pretty good, but there seem to be some similar products on the market that can convert locally without uploading. I’m all for fun side projects, so don’t take this the wrong way. Does this have a practical use case? Like are people actually wanting to make their PDFs less legible? Usually I’m trying to do the opposite, clean up my scanned-in documents. Charles Schwab, the brokerage, didn't like that my signed form retitling an account looked too perfect (I had scanned my signature and then inserted the JPEG into their PDF form, which is absolutely 100% legal as a signature). So I printed the form out and sent them a picture of the printout. They didn't like that, either. So I moved my money out of the account. That worked fine. I've been in situations where I had to supply a digital version of a signed document but the person asking for it required that it be physically printed off to be signed and then scanned back in. Some policy thing. I think it would technically be fraud to use this but that's one use I thought of. The description however seems like the creator just likes how scanned documents look. They describe it like how analogue music fans describe vinyl records. I guess everything is nostalgic to someone out there eventually. This is in fact useful for people who demand you to print out and sign contracts. Did so many times in the past, using some ghostscript+imagemagick scripting to avoid the cargo culturing. I was actually required in the past to "print, sign and scan", and due to my lack of a printer I just took a picture of my signature and pasted it in. Nobody ever complained, but if they did, I imagine I'd rather use something like this than go to a copycenter to print a single sheet of paper to satisfy some arbitrary requirement. For some value of practical, I could see it being useful in making handouts for an RPG where the handout is supposed to be a photocopy of a section of some rare book the players need to scan for clues. I sometimes want to create PDFs that contain text (Python code) that is not selectable. I want my students to type it in, not copy and paste. I don’t know whether this tool enables that, but the idea is in the neighbourhood of “make it look scanned”. iOS will natively let you select the text, as it does ocr on ever image. Maybe Android does the same. There are countries such as France that request plenty of nonsensical handwriting with some weird also handwritten formulas. This comes from the times where graphology was a big thing in France (you would usually be required to send a handwritten letter of motivation). Poland is also strong on that, requiring "readable handwritten signatures". This will end when the dinosaurs that still feel it is important go away. Typically when I send a form I will do as much as possible in a PDF editor, including the signature. Most of the world is in denial about how electronic documents, especially scanned ones, work, so you have to play along to stop them from getting upset. Yes. Fraud. It makes a document look like it existed in physical form. Imagine for example a purchase agreement for a house that was physically scanned. You could change the signature to a different name and then make it look like it was original. I am not asserting the authors intent is to facilitate fraud or there isn’t any other practical use, but let’s not be naive and act like fraud isn’t a likely use. Before you downvote at least respond with why you think my analysis is wrong. It's not that you're wrong, but the fact that it would be fraud is farcical and needs to be challenged. My bank demands that I perform this ridiculous hoop-jumping. Like others here, I use ImageMagick hocus pocus to defeat them with trivial ease (a couple of times they complained so I tweaked the algo a bit and they were happy). The whole situation is beyond absurd. It's security theater in place of security. This is fraud. Your are passing off a document as authentic by misleading use of visual artifacts to make the origin of the document appear different than reality. Just because you don’t like the security theatre does make it acceptable to misrepresent the origin of a document to satisfy the security requirements. And I gave a specific example, slipping a page into a document that wasn’t in the original and making it look like it belongs by making it look scanned. Imagine I changed the purchase price on your home to 10% of its value rather than the original agreed price and took it to court to enforce the purchase. This tech would make that appear more credible. An interesting take that reveals differing moral bases. As a preamble, I have zero moral qualms about technically committing fraud in order to access my own money (almost nobody would). More important, I choose not to respect a law that upholds an insecure and broken system. A parallel with traffic regulations come to mind: as a cyclist I regularly break rules when I consider that they do not best serve my safety. All things being equal, I follow the law. But all things are not always equal and bad laws are there for the breaking. The correct outcome here is that the law is tested and amended. That is the way to end the perverse situation of the precise example you raise, where anybody with technical skills can fake a document and then win in court. Hard disagree. Just because you don’t understand the rationale of a law doesn’t mean it is arbitrary and disconnected from your safety or best interest. I’ll give a concrete example. In law school I was hired to write a memo on a traffic circle. There was a very deliberate and effective approach to identifying where pedestrian crossings were the safest. And the cross walk itself is an attempt to encourage people to go to the safe areas for crossing. Cross walks also create a clear zone of liability. If a driver hits a pedestrian in a crosswalk they are deemed at fault. Outside the crosswalk the pedestrian is deemed to have contributed. So the law incentivizes both driver and pedestrian behavior to converge on a known safety pattern in the safer section of the road. So you can jaywalk based on your analysis that it isn’t really that big of a deal or necessary for your safety but at the scale of society the law encourages the safest behavior. As far as signatures. I would agree there are better systems. But they still serve a valid function. I had ATT forge mysignature on a contract to try to get me to have to pay an early termination fee. But because I had other documents with my signature I was able to demonstrate that the forgery wasn’t even close to mine. I would honestly rather have that rather than a digital stamp or Docusign. I never said that the act of making a digital doc look like it was scanned is fraud. I said that process would be used in other fraudulent acts. You could just as easily edit it, print it, then scan it again. This tech doesn't enable you to do anything you couldn't already do. The real problem is that written signatures are a poor form of authentication. Everyone is overlooking the reality that multiple parties have a copy of the documents, and a judge is not going to believe that the seller agreed to 10% of market value when they claim otherwise and they have a document backing it up and so does their lawyer and so does their real estate agent. And you are going to be charged with a crime if you attempt something like this. There are plenty of examples of a single set of documents with no corroborating documents. In fact, when I was a lawyer for Lehman in 2008 most mortgage transfers were a line in a spreadsheet not a legal document. Many wills have only a single copy that was kept in a safe deposit box. I could go on and on. The fact remains that altering a photocopied or faxed copy of a document has been trivially easy for decades and yet it's not really a problem in real life, because it's a criminal act to do so and present it as authentic. Just because there is an alternative path doesn’t mean this path won’t equally facilitate fraudulent acts. That is an example of a flawed argument named false equivalence. And it ignores that the this library eliminates the friction of printing, and enables the ability to scale the process. Print - sign - scan. I've never been told to keep the physical print out. I've also never had someone refuse my too-perfect digitally inserted signature, but I could totally see it happening. Oh and I don't like signing stuff anywhere, so I also used my scanned signature and got a custom stamp made. :) Is there any good tool that does the opposite — turning scanned documents into clean PDFs? I’ve had that need recently. But… does it look scanned? https://i.imgur.com/ENKZV7s.png You can play around with the sliders to obtain results that look more dramatic: https://cleanshot.com/share/gpfyJyJV Much better than your current demo image! The default vignette is too obviously digital If you’re interested in another suggestion: maybe allow image output too since that seems to be one of the steps in your pipeline? Maybe for some people using the jpg or a png directly is better than the final pdf. Basically, you’re converting it to an image-based PDF so they cannot just scrape the text off of it but would have to use OCR? In the example image, the edge gradient bevels give it away. There might be extra stuff that can be done to remedy that with this tool, but I'm not sure I'd ever use this anyway. Everything can be adjusted, that mostly comes from `--paper-tone` being set too high. Thank you for making this a free tool. There are too many PDF tools that are unnecessarily paywalled, or have a paid tier that don't make any sense. We need more tools from paid ones that should be completely free and OSS.
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