ZX81 BMP converter

[kolbeck]

Hi,

Announcing an ALPHA version of a ZX81 screenshot converter. It takes a BMP (from EighyOne or SZ81) and converts it to the following formats:

• .s81 for standard non-hires ZX81 screens (a sequence of 768 character codes from the ZX81 charset)

• .scr for hires screens with regular size (in ZX Spectrum display format)

• .png for big screens, that goes beyond the 256x192 size

• .txt for ASCII (with control codes to implement inverse print)

You can find it here: https://zxinfo.dk/scr/ - just remember it's still in an early phase.

For ZX81 charset mapping find it here: https://en.wikipedia.org/wiki/ZX81_character_set. For big screens, take an a look at MaxDemo here: https://spectrumcomputing.co.uk/entry/32034

[mention]4thRock[/mention] , [mention]moroz1999[/mention] , [mention]R-Tape[/mention] , [mention]Einar Saukas[/mention] . [mention]pavero[/mention]

/Thomas

[4thRock]

Very interesting!

I guess this might also work for the ZX80, if you account for the different character set:
https://en.wikipedia.org/wiki/ZX80_character_set



(Sorry for the late comment but I've been in places with no internet or mobile network!)

[Einar Saukas]

It works perfectly, thank you!!!

Perhaps it could also accept SCR or S81 as input, to generate the other formats?

[Einar Saukas]

Here's a simple program for the ZX81 16K. Load a S81 file to memory address 30000, then run the program to see it on screen:

Code: Select all

10 LET D=PEEK 16396+256*PEEK 16397
20 FOR R=0 TO 23
30 FOR C=0 TO 31
40 POKE D+R*33+C+1,PEEK (3E4+R*32+C)
50 NEXT C
60 NEXT R
70 GOTO 70

[kolbeck]

Very interesting!

I guess this might also work for the ZX80, if you account for the different character set:
https://en.wikipedia.org/wiki/ZX80_character_set



(Sorry for the late comment but I've been in places with no internet or mobile network!)

It will work for ZX80 as soon as I get the mapping for the charset done

[kolbeck]

It works perfectly, thank you!!!

Perhaps it could also accept SCR or S81 as input, to generate the other formats?

Great idea - will put it on the TODO list.

/Thomas

[4thRock]

Just one more thing
SCR export doesn't use bright. That's correct because of ZX Spectrum attribute limitations on the border area.
But PNG export is using full bright white. I understand why buy it's somewhat inconsistent.
Could you change it to #CDCDCD (that's what we are using for non-bright white) ?
It would allow back and forth conversion with consistent results.

[kolbeck]

PNG is for now a simple convert of the BMP, so whatever the emulator produces. Another example is if you have TV artefacts enabled in EO, then the PNG Will have scanlines.

/Thomas

[kolbeck]

Just one more thing
SCR export doesn't use bright. That's correct because of ZX Spectrum attribute limitations on the border area.
But PNG export is using full bright white. I understand why buy it's somewhat inconsistent.
Could you change it to #CDCDCD (that's what we are using for non-bright white) ?
It would allow back and forth conversion with consistent results.

[mention]4thRock[/mention] - can you please try again with your BMP? Just testing a concept, and would like to hear if that is the right direction.

[4thRock]

@kolbeck, now I get a PNG that looks the same as the SCR (non-bright)
So yes, that's what I had in mind.

[kolbeck]

The ZX81 screen converter https://zxinfo.dk/scr/ now goes into BETA.

Now supports the following formats as input:
* .bmp as produced by various emulators (e.g. EightyOne and SZ81)
* .a81 for standard non-hires ZX81 screens (a sequence of 768 character codes from the ZX81 charset)
* .scr Widely used screen format used for ZX Spectrum (ZX81 hi-res)

And converts to the following formats:

png, scr, a81 & txt (the txt format makes it easier to copy/paste text, in case that is required).

Next I will be adding support for ZX80 screen dumps.

Any feedback is appreciated - thanks!

/Thomas

[Einar Saukas]

This is great!

Is there any reason to name it a81 instead of s81?

[kolbeck]

a & s - left, right, right left - sometimes I mix them up

It's been fixed now

[Einar Saukas]

Thanks

[pavero]

Maybe small improvement. It doesn't work for BMP files without a border - 256 x 192 pixels only.

[Solaris104]

Some screenshot from EightyOne need correction.

[kolbeck]

Maybe small improvement. It doesn't work for BMP files without a border - 256 x 192 pixels only.

I’m not aware of any emulator that only outputs 256x192- sz81 can however output dumps double the size, which is handled. I will look into the 256x192 that in the future.

[kolbeck]

Some screenshot from EightyOne need correction.

There’s no way of correcting that automatic, but the screens you show are exactly for the purpose of identifying screens that needs correction. A lot of the 1k hi-rea games needs correction, so parameters for offsetX and offeetY will be implemented in the future

[pavero]

Maybe small improvement. It doesn't work for BMP files without a border - 256 x 192 pixels only.

I’m not aware of any emulator that only outputs 256x192- sz81 can however output dumps double the size, which is handled. I will look into the 256x192 that in the future.

Just EightyOne can do this, if you set Border Size = none.

[kolbeck]

I’m not aware of any emulator that only outputs 256x192- sz81 can however output dumps double the size, which is handled. I will look into the 256x192 that in the future.

Just EightyOne can do this, if you set Border Size = none.

Ahh- thanks, will take care of that

[kolbeck]

Maybe small improvement. It doesn't work for BMP files without a border - 256 x 192 pixels only.

Hi [mention]pavero[/mention] - please try again, it should now support all sizes from EO

* No Border: 256x192 pixels
* Small Border: 264x200 pixels
* Standard Border: 320x240 pixels
* Large border: 400x300 pixels
* Full frame: 413x312 pixels

The PNG will of course have the same size as the input file. Also for large and full frame, the adjustment is not 100% correct - looks like the actual dump is not centered Will be fixable when adjustment parameters are added.

/Thomas

[kolbeck]

Some screenshot from EightyOne need correction.

[mention]solaris104[/mention] - please try out the added correction parameters

/Thomas

[4thRock]

* Full frame: 413x312 pixels

Interesting. 312 lines seem to be the full extent of the generated TV signal, including non-visible sync lines:

( http://blog.retroleum.co.uk/electronics ... -voltages/ )

[kolbeck]

I have not seen any full frame programs yet, maybe a little challenge for our experts?

[Solaris104]

@solaris104 - please try out the added correction parameters

/Thomas

Thank you, it's works