prepairing old magazine pcb    scans for laser toner transfer printing - Page 1
Forum section: electronics / beginners

author: p.larner
author_rank: Frequent Contributor
timestamp: March 05, 2024, 08:39:22 pm
content: I have a few magazine articles for projects or scans of,if i print pcb track layouts to then scan and flip,they are not 100%b+w but grainy,this makes toner transfer dificult as they print in greyscale not b+w,is there any way to fix this,ie image editing etc,so its a defined b+w for toner transfer method,i hope folks understand my issue?,thanks in advance.

author: Jwillis
author_rank: Super Contributor
timestamp: March 05, 2024, 09:06:03 pm
content: Depends on your printer. What brand and model is it. Check the configuration. Does it have toner saver options, dpi (dots per square inch) resolution settings, Are you using monochrome only options, Can you turn up toner saturation in monochrome?I don't use the toner transfer anymore because because I find the liquid photo resist method works much better than both toner transfer and photo-resist film.

author: Benta
author_rank: Super Contributor
timestamp: March 05, 2024, 11:08:48 pm
content: If you have the scan in a sensible format, touching up the black (and white) areas in a drawing program is a piece of cake.

author: Andy Chee
author_rank: Super Contributor
timestamp: March 05, 2024, 11:38:19 pm
content: Quote from: p.larner on March 05, 2024, 08:39:22 pmJust to clarify, is the original image greyscale? If so, then convert the image to b&w using image editing software. You can use the histogram tool to adjust for the best b&w image. Inevitably though, you'll have to manually do minor touch ups to the image yourself.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 06, 2024, 12:58:48 am
content: There are a variety of options. Most photo editing software has multiple options for adjusting contrast and getting pure B & W images. If you haven't already locked in on this class of software GIMP is a good option, and free. There will be tools to adjust the histogram, thresholding tools and tools to adjust the gamma. Also noise filters, filters to remove the silkscreen pattern used when the magazine was printed and others. Each image will benefit from different combinations of these techniques.Don't ignore smoothing the image. Pure thresholding can leave jagged edges on lines and holes in the middle of dark areas. Upping the pixel size of the image, and running various filters (I find a Gaussian filter possibly the most generally useful) before thresholding and reducing to two colors can generate smoother traces.Also, a vector editing program such as Inkscape (also free) can be useful. They have tracing tools that attempt to find and follow edges, which results in clean lines, not grading from black through white along the edges. There are tutorials in this forum on how to trace PWBs using Inkscape, and many of the techniques would work fine for cleaning up magazine images of PWBs.Finally, be sure to check the geometry, including both scale and warping. For older PWBs that are mostly Rs, Cs, Ls and transistors or fets this won't be too important, but the publishers editing, printing and distributing process, followed by scanning and editing can easily result in pad spacings that don't fit large components like CPUs and connectors. The geometry errors are relatively easy to correct by scaling using the known sizes of these large components. Warps and twists are a little tougher, but once you are thoroughly familiar with the editing software of your choice it isn't terribly hard.

author: Jwillis
author_rank: Super Contributor
timestamp: March 06, 2024, 08:34:22 am
content: Sorry. Obviously I misunderstood the question. As others have said that photo enhancement software will work for you. There are online AI enhancement tools and other services available to as well that have free trials.

author: p.larner
author_rank: Frequent Contributor
timestamp: March 07, 2024, 12:20:22 pm
content: i will clarify what i mean,as is printing a scan results in the background being printed a sort of off white so toner is printed all over the paper not just black where the tracks are,as is it makes it usless for tonner transfer as toner gets printed for the whole document not just where the tracks are.

author: SeanB
author_rank: Super Contributor
timestamp: March 07, 2024, 12:34:08 pm
content: You need to edit it, at a minimum crop to selection, then you convert the image to a grayscale image, and then you adjust it to be right.Gimp Image, mode and select greyscale. Then colours and exposure, and use the histogram sliders to turn it into a hard black image, with nothing in the histogram other than those 2 peaks of all black or all white. Then you can print it, no toner saver, and use it like that. Scale a little if your scan is distorted, to get it right, and make sure when scanning to have the page held flat against the platen glass, so as to not have waves.

author: Zipdox
author_rank: Regular Contributor
timestamp: March 07, 2024, 10:00:34 pm
content: Quote from: p.larner on March 05, 2024, 08:39:22 pmYou just have to to increase the contrast.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: March 07, 2024, 11:06:43 pm
content: Play around with ImageMagick. It's bound to have a setting where you can make an image black and white (not greyscale) and pick the threshold between black and white.https://superuser.com/questions/893476/converting-from-color-to-true-black-and-white-in-imagemagick

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 08, 2024, 01:01:37 am
content: I will expand. There are many, many failings on these old magazine scans. And at least here in the US there was a period when the magazines took steps to make their pages hard to copy since they felt threatened by the photocopier revolution of the 70s and 80s. Fortunately those copy prevention techniques weren't usually used on PWB layouts and died off completely for a while before the magazines themselves died. But they rarely made the backside of the page blank so all of these things can bleed through the thin paper often used (one of the anti-copying techniques in addition to a possible cost savings).For some cases a simple solution like using the automatic conversion to to a 2 bit black and white image that is included in most image editing software is enough.Others require a manual thresholding operation. And this may require shading across the image as there is an intensity gradient that has been introduced somewhere in the reproduction chain. Histogram equalization helps in some cases, in others playing with the gamma function (basically a non-linear amplitude gain) can help.Depending on the initial resolution of the image and other factors such as compression artifacts these thresholding operations may result in jagged edges or even breaks in narrow traces. There are several ways to resolve this, including using low pass spatial filters, edge finding filters, manually touching up and others. Manual inspection for these breaks is tedious, and for me error prone. To assist in automating this inspection I use the flood fill function to fill traces with a contrasting color. Breaks where the fill doesn't reach the end of the trace become obvious. With judicious addition of boundaries (in a contrasting and easily removed color) can also let you flood the spaces between traces. A flood fill that crosses a trace clearly indicates a break.These cases also can benefit from the bitmap to path conversion in Inkscape which uses several of these techniques semi-automatically, though there are thresholds which can be adjusted for best results.I have even found some cases where the available image is so bad that starting from scratch is the easiest approach.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 08, 2024, 08:45:44 am
content: A different approach is to load your images as a background into KiCad. That way you can use them as a reference while re-creating the PCB. It is a lot more work then using some photo manipulation program, but as a result you will have a complete project (enter the schematic too) that you can modify if you wish and create gerbers to order PCB's.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: March 08, 2024, 10:28:53 am
content: Quote from: Doctorandus_P on March 08, 2024, 08:45:44 amI completely agree with Doctorandus, you are far better off creating a fresh clean PCB layout using a scanned image as the basis for the layout. I use Sprint Layout 6, which also has an image overlay feature. You then place your components and tracks.Personally, I have given up home production of print boards, having them professionally made in China is so much better and very cheap. Costs are as little as 5 GBP for 5 boards, including tax and delivery to the UK in 14 days with JLCPCB... Why bother with home production at those prices, zero mess and no chemicals to dispose of.SJ

author: tooki
author_rank: Super Contributor
timestamp: March 08, 2024, 02:25:01 pm
content: Quote from: CatalinaWOW on March 08, 2024, 01:01:37 amPro tip for scanning thin paper with bleed through of the reverse side: use a flatbed scanner and place a sheet of black paper behind the sheet you need to scan. This makes the background darker, but importantly, it’s darker everywhere, which means a simple global contrast/curves/histogram adjustment is all that’s needed to fix it right up.