DIY tablet computer, maybe.

[S. Heslop]

I'm not great at programming.
...
Gives me something to think about while I type out this stupid function 15 more times.

Number one rule of programming: Avoid duplication.

At college the first thing I ever wrote was a calculator that was entirely if statements. I was pretty proud of myself. So proud that i've continued the theme and now when I occasionally write something I just come up with a big block of if statements to cover every possibility.

I do think something along the lines of an array that stores all the keypresses then does a for statement for each while checking for changes might be more elegant. There's probably something even better too.

[vtsteam]

Sorry I missed the first assembly and use on this one, Simon -- don't know how. Congrats!!!  Looks great, and seems to work that way, too! 

[S. Heslop]

Sorry I missed the first assembly and use on this one, Simon -- don't know how. Congrats!!!  Looks great, and seems to work that way, too! 

Thanks very much! I've also used it a couple of times to ink pictures. I'm still not great at inking but being able to follow the sketch lines on screen really does help.

[S. Heslop]

Had a busy day yesterday driving all about. Managed to return that CPU though with no fuss. I'm a little annoyed they sold me a broken CPU in a paper bag but returning it was fairly painless. Although they've gone paperless so the guy taking the chip and telling me that it's all sorted and the receipt was emailed was a little concerning. As much as I don't care for modern smartphones I guess you really need one to function these days.

[S. Heslop]

Here's something i've been working on.

I did a digital painting, since that's very convenient. I think it turned out alright.

It's fairly corny but I like corny.

Then it was projected onto a canvas with... a projector. So I could transfer the lines.


And i've begun painting it in acrylics. I think I need new brushes since these ones i've got don't seem so great. Very bristly and hard to control the flow.


But something that bothers me is that I spend more time mixing colours than I do actually trying to slap down paint. From what i've heard that isn't unusual even for experienced painters. Another side is that trying to match colours to those on a monitor is tricky since monitors can of course produce way brighter and more vivid colours, and as the day goes on the lighting in this room changes.

So i'm thinking about some sort of dispenser that squirts out blobs of paint in the right proportions to match the selected colour on a display. I really like the idea of automating out all the tedium and skill in painting. It'd be great to come up with some sort of system so you're effectively painting by numbers but fooling everyone.

[S. Heslop]

So you can get the 3 colours of the CMYK colourspace in paints, called Process Magenta, Process Cyan, etc. Artist paints have some pretty cool names, like Naphthol Red. They all sound so dangerous - way cooler than house paints with fruity names like Cherry Desires and Volcanic Dream.

But yeah if CMYK gives me a value like #00d9cb9c which describes cyan, magenta, yellow, and black then... what about white. Or transparency. Would it just be the 1024 (or 1023. or 1020??) with those 4 values subtracted?

I should pick up some syringes too and experiment a bit!

[tom osselton]

I use to be a journeyman offset pressman we had a colour book that told us the ratios, there has to be a chart somewhere on line or possibly from the makers of your paint.

[S. Heslop]

That must've been an interesting job. Printing is something I want to try at some point, and I've read a little into lithography and i'm always amazed it works as well as it does even in its basic form. It seems like there's alot to go wrong on a big offset printing press.

As for colour charts. The program I use (and I assume most painting programs) gives you the CMYK values in hexadecimal when you select them.


Now I'm wondering how to best dispense the paints. The obvious way is just a stepper motor and screw pushing a syringe with a narrow blunt needle but i'm not sure how precise that'd be for small amounts. There's plenty to read on dispensing pastes though, between all the solder paste dispensers and ceramic 3d printers out there. I'd also like something that really jets the paints out so they don't ball up on the ends of the nozzles and need wiping.

[PekkaNF]

Interesting concept.

You have calibrated your monitor (RGB)?

You realize that diferent color systems (additive vs. substractive vs. paints) can not really be 100% matched and your take on them will depend much from ambient color. Simple test is to mach screen to spraypaint inside (artificial light) and then roll out canavas to evening/morning light and wonder how they look that diferent.

https://www.color-management-guide.com/introduction-color-management.html

Pekka

[S. Heslop]

I haven't calibrated my monitor beyond going by eye. I figured you'd need one of those fancy probes to do it properly. It's something i'd also never assigned a huge priority to since the way you see things is very relative. That pen tablet display is a little on the cool side, and after staring at it for an hour and going back to this monitor everything seems quite pink.

But yeah that's exactly the problem i've had in trying to match colours to a monitor. I think the reason still lifes were and still are a popular painting subject is because you can control the lighting for as long as you need to paint. I can think why else the world needs another painting of fruit and vases. Perhaps a smarter way to go about matching a picture would be to print it out and match colours to the print. I still think there's too much Art involved in mixing the colours themselves though. Last night I got a little psyched thinking about this since it went from something I was considering sort of as a joke to something I think could actually be useful.

[S. Heslop]

What a waste of fuel and daylight. Went all about looking for syringes with blunt needles. Doing a google search suggested that vape shops stock them since people use them for refilling and mixing their liquids, but nowhere actually had them in stock. Tried to find a medical supply store but looking now I went to the wrong place, a first aid training company, that was closed. Still trying to figure out how I made that mistake. I thought I knew where it was.

[S. Heslop]

I did pick up the paints though. Tried mixing them close enough by hand to the proportions I imagined would work and came out with a very neutral grey instead of a deep salmon red. I think it's gonna require more thought and reading.

Mixing half and half of cyan and yellow yields the colour i'd expect. Mixing a third (in total) of white to that yields about a 50% yellow and cyan each (on the colour sliders in this program). But trying to mix in black really throws it off. Of course these arent accurately metered portions, and while i'm aware they wont be a complete match i'd expect them to be close enough to recognise.

Searching about finds alot of angry message board people yelling about the guy asking the question not understanding how printers work then proceeding to explain something separate to what the guy asked, which is a common theme on those stack exchange type websites.

[tom osselton]

What a waste of fuel and daylight. Went all about looking for syringes with blunt needles. Doing a google search suggested that vape shops stock them since people use them for refilling and mixing their liquids, but nowhere actually had them in stock. Tried to find a medical supply store but looking now I went to the wrong place, a first aid training company, that was closed. Still trying to figure out how I made that mistake. I thought I knew where it was.

Have you tried a pharmacy for syringes I’m not sure you need needles but they have them too.

[S. Heslop]

What a waste of fuel and daylight. Went all about looking for syringes with blunt needles. Doing a google search suggested that vape shops stock them since people use them for refilling and mixing their liquids, but nowhere actually had them in stock. Tried to find a medical supply store but looking now I went to the wrong place, a first aid training company, that was closed. Still trying to figure out how I made that mistake. I thought I knew where it was.

Have you tried a pharmacy for syringes I’m not sure you need needles but they have them too.

That's so obvious and I just... never considered it. I'll take a look tomorrow. I got some 10ml syringes ordered from amazon but i'd like to get some 1ml ones for easier hand mixing without wasting alot of paint. Thanks for the suggestion.

[S. Heslop]

Done a bunch more searching and found nothing but nonsense. Plenty of people are asking this question and it seems if they ask computer people they get basic explanations of colourspaces, and even more esotetic explanations of stuff like how the eye evolved (???) but they don't answer the actual question. And if they ask art people they get a bunch of people saying 'learn to mix colours the old fashioned way! Dedicate your life to learning this redundant skill!'

So thinking about it myself. I figure if it's 100% magenta then thats 100% of the magenta obscuring the white underneath (or maybe more like 90% in reality to not soak the paper). And if there's 50% cyan on top of that then theres still no white in that. But if its 50% magenta and 50% cyan then thats 50% of the white showing through, so the white is the percentage left over from the largest percentage of any colour.

But then printer inks are transparent and not opaque, so even if it was 100% magenta then some of the white will be showing through. Maybe. But either way that gives me something to test tomorrow, and maybe gets me in the ballpark where I can calibrate out quirks in the medium. Assuming i'm correct at all.

I also feel that since colour perception is relative to their surroundings then i'm more worried about their relations than total accuracy, for now at least. If I end up with something that has more or less contrast or a different gamma curve (or whatever you'd call the reflective equivalent) than whats on the display (in ideal lighting) then I think that'd be entirely satisfactory as long as the colours relate.

[Brass_Machine]

Jeez... I don't pay attention for a little while and you have gone and built it!

I like the layout and it looks pretty good. I would like to build something similar... I would like to build a portable game emulator. I have a small android one right now, but it cannot emulate some of the games I wish to play.

Nice job!

Eric

[S. Heslop]

Thanks Eric!

The last electronic device that ever impressed me was Sony's first PSP, with homebrew of course. It was impressive playing SNES and Megadrive games but when they brought out the PSX update (and it got cracked) that really blew my mind. It wasn't long after that when they brought out the iPhone and electronics never recovered.

I know the Raspberry Pis are fairly popular for emulating games, there's alot of stuff for that and they're pretty damned cheap. Having a look it seems they struggle with stuff like the n64 and Playstation, but they seem to run alot of the weirder stuff like the Wonderswan and Amstrad CPC. There's of course other Raspberry Pi like devices but from what i've read they don't get the same level of support and aren't a whole lot better. But i'd imagine the x86 based single board computers would emulate a whole bunch of games pretty well and have access to the whole gamut of emulators out there.

Shame the CD-i gets no love. It's not a good system but it has one extremely cool and weird game, Laser Lords, that's hard to play since there's no great emulator for the CD-i. I admire any game with an intro cutscene calling you the Chosen one who gets to wear the sacred robes, then one of the first guys you talk to says 'oh another one of you losers, I recognise the uniform'. And any game with multiple Peter Lorre impersonations. It's really full of neat ideas and surprises.

[S. Heslop]

I'm all set to make one of those creepy children's youtubes. Isn't it great to live in a world where we get to see what childrens entertainment would look like if it were produced globally with absolutely no regulation or accountability.



This is the target colour. I kinda forgot its CMYK value but it was something like 85% magenta, 75% yellow, and 60% black.



And here's what I get if I mix it as .85ml magenta, .75 yellow, .60 black, and .15ish white. Or as close as I can get with a 10ml syringe.


I mixed the 3 paints before adding the black since I suspected that'd be overpowering.


And this is what it should look like. 


Looking at those blobs it seems like I dispensed about the same amount of yellow, or maybe even a little more, than magenta. So I wasn't really that accurate with the dispensing. The colour in that jpeg of the paint, averaged out, is M76, Y81, (and K31). Which is probably within the tolerance of what I can dispense and the white balance of the camera.

But i'm still confused. I think i'm going to get some smaller syringes so I can hopefully dispense more accurately. I also realise that different paints will probably have different pigment amounts. I should probably also consider how I can actually measure the colours more accurately so I can maybe get some actual data to compare.

Although it does frustrate me that this is clearly already a solved problem. But hell if I can find anything about it on the internet.

[S. Heslop]

So much for that. The chemist closes at 1 on a saturday. I went to look at camper vans instead.

[S. Heslop]

God damn. I bought some cables to try hook the tablet display to my desktop PC for convenience, and just as i'd feared it broke the drivers. Now I got no tablet!

Really i'm now just thinking if I want to uninstall the wacom drivers or the flaky chinese drivers to hopefully get one of them working. It'd be nice to have the display but the pen that goes with it isn't so great. And I could still use it as a regular graphics tablet on the main monitor by changing some settings in the drivers.

More than anything though i'm a little angry Windows isn't able to support multiple tablets. It can for mouse stuff but not for drawing stuff. But I imagine the exact thing I want to do isn't uncommon. Small cheaper pen display for inking and a larger better calibrated display with a regular tablet for colouring and painting.

[S. Heslop]

Well now nothing is working! Even lost my mouse for a bit. I've got so much junk installed on this computer that I think it might be time for that long overdue reformat.

[S. Heslop]

Reinstalling Windows 7 was a 2 day adventure. And I mean 2 full days. But i've finally got things set up for the most part (still need to try import or recreate some of my brushes in Krita).

But hey it works real good. It's alot more responsive on the desktop. Issues that I thought might've been the chinese display controller or the microcontroller emulating a wacom board at first, but I guess the laptop just wasn't quite powerful enough for krita. That said it was an absolute godsend when reinstalling Windows.

BUT. Now I've gotta do something about that pen. It's so thin and only has the one button. I could easily drill out a bit of wood or delrin to slip around it, or 3d print something, but i'm thinking about adding more buttons with maybe an IR transmitter on the tip. I'd be worried about RF stuff interfering with the digitizer.

The real question though is how many buttons can you practically fit on a pen. And how many would be useful.

[S. Heslop]

I've been drawing a bit more on this pen display. It's all I got now! But i'm starting to notice more cracks in it. The pen doesn't have very good pressure sensitivity, and looking into it it seems that's quite normal for pen enabled laptop displays as they have a low pressure resolution. It still feels like a step up from the other tablet now that i'm getting used it it.

But the pressure along with the lousy viewing angles and inconsistent colours of the TN panel (not to forget the relatively low display resolution) had me looking into other displays again. Reading more of the bongofish forums also suggests that their DIY Cintiqs, fantastic as they are, tend to have jitter issues. Not always but it's a common enough occurance to make me hesitant to really spend money on trying to combine a fancy display with a fancy tablet.

So i've been looking at those Chinese pen enabled displays again. They range from 10 inches up to 22 inches in steps of approximately 2 inches, with prices ranging between £200 to £500. There's a full HD one at 13.3", IPS, which costs about £230. Still more money than I have but it's not far off what trying to get a useable modern laptop display would cost.

Also looking at the arrangement i've settled on for the display I made, with it quite close to vertical on the desk, I was thinking I could easily fit a relatively small computer behind it. Then thinking about how to fit a keyboard to it I was considering something that slides about or is maybe detachable and covers the display in transit... and suddenly I realised that i've reinvented the luggable computer.

[PekkaNF]

I remember those luggable computers. They were really usefull (but short lived). I was over the moon to get one of them, because Siemens S5 et.al. needed a proramming device (Siemens Simatic S5 PG 675) that was really big/unconfortable/heavy to carry AND they were pretty expensive and unusual. Really pain when you need to travel with them, specially to places like oriental countires, USSR and USA with their higky bureacratic and suspicious customs officeers.



How come it looks relly small on pictures....It felt huge when you lugged trough airport, showed in customs, show and tell ATA-Carnet and prepared to spend some extra time anything from 11 to 6 hours in customs AND every country had it's own customs and procedures. EU is joy 0 sec on customs instead of 1 hour on German customs, then 2 hours on French customs and after a week same thing but trough Swiss customs. My personal record was 2 km, journey from Russia - took 10 hours and six offices.

Don't plan to travel with DIY looking computer

[awemawson]

Pekka that's EXACTLY the device with Step5 software that I need to read my Symatic 820T PLC ladder