Adjusting an Image Saved from VICE

Post by **Jeff-20** » Sun Mar 06, 2011 4:48 pm

I would like to save a game screen image in VICE and adjust the proportions to make it look as it would on a CRT 4:3 monitor. VICE saves the PNG at 416 x 253. Does anyone have any approximate dimensions that would read true to a real VIC screen? I'll be adjusting in Photoshop.

Mike · Post by **Mike** » Sun Mar 06, 2011 5:02 pm

That depends on the TV system.

On NTSC VIC-20s, the pixels have an aspect ratio of 1.33:1, while on PAL they are longer, roughly 1.67:1.

If you take the standard 2:1 output of VICE, you can approximate these aspect ratios by resampling the picture to either 277 x 253 (NTSC) or 347 x 253 (PAL), preferably with a Gaussian filter.

Greetings,

Michael

P.S. Here's an example for PAL output where I cropped the border after resizing the screenshot. I used IrfanView for this, though:

P.P.S. VICE set to PAL output writes a 544 x 284 image. Here you should resample to 363 x 284 (for NTSC) or 453 x 284 (for PAL).

Boray · Post by **Boray** » Sun Mar 06, 2011 5:34 pm

Why not set the option "true aspect ratio" in vice 2.3, then press Alt-Prt Scr. Open Windows Paint. Press Ctrl-V. Crop it a bit and save it.

Post by **Jeff-20** » Sun Mar 06, 2011 7:52 pm

Boray wrote:Why not set the option "true aspect ratio" in vice 2.3, then press Alt-Prt Scr. Open Windows Paint. Press Ctrl-V. Crop it a bit and save it.

Because I've been still using VICE 2.2.

Time to update.

The hard part is that VICE puts an uneven border around the image. It makes the ratio a bit of a guess. I'll try your suggestions.

Mike · Post by **Mike** » Mon Mar 07, 2011 4:09 am

Boray's method also works in VICE 2.2, if you activate 'keep aspect ratio', set it to '0.667' for NTSC and '0.833' for PAL. These values relate to the standard display method of double-width pixels.

You'll then also need to activate the PAL emulation to even out pixel widths. It's just I very much like to apply my own filter method.

Furthermore, I do not know where the VICE developers derived the value '0.842' from. Some time ago, I took a CRT TV, from which I knew it displayed a proper circle with a standard test image from a TV station. I measured width and height of the white VIC display area, took 22 columns vs 23 rows into account, and ended up at a value of 1.67, give or take 0.01.

And, regardless whether you chose Boray's method or mine, the screenshot won't reproduce the checkerboard patterns, which are the result of mixing chroma and luma in the video circuitry on the main board - which the S-Video mod tries to eliminate.

Michael

P.S.: could one of you please move this thread into the 'Emulation & Cross-development' section? Thanks.

P.P.S.:

Because I've been still using VICE 2.2. Time to update.

I'm still using WinVICE 1.16. This is sufficient for 99.99% of all the programs around. I installed VICE 2.3 just to reassure myself it still doesn't give me a good reason to upgrade.

Boray · Post by **Boray** » Mon Mar 07, 2011 6:54 am

More about this:
http://sleepingelephant.com/ipw-web/bul ... php?t=4413

rhurst · Post by **rhurst** » Mon Mar 07, 2011 2:46 pm

... it still doesn't give me a good reason to upgrade.

Heresy. I take it you don't run Mega-Cart on VICE then?

True for xvic, but the VICE project has done a lot of incremental improvements that have been beneficial to all its emulators, specifically, video output using SDL or OpenGL had been pitiful until the 2.2 release, while 2.3 takes it a step further with CRT emulation doing a fine job. Sound processing is much more stable and includes pulse.

So the heavy-lifting is still centered around x64 and now x64sc. And that's where it probably belongs, given the rich history and user following of C64.