Apple IIgs Super Hi-Res (SHR) Converter Output Comparison – A2B and Convert3200 - Summer 2015

This article compares the external segmented palette output from A2B Version 7.0 to the default output from Convert3200. (A more advanced implementation of external segmented palette output called “full palette conversion” is currently under development. In the meantime what you see here is A2B’s best output).

For those who have been following A2B’s ongoing SHR development, external segmented output from A2B is not Image Tone Rendering; Image Tone Rendering uses the idea of a single tone for the whole image and external segmented output doesn’t care to group and reduce its colors to the global tone of the image and instead uses the tone of each segment and tries to include as many colors as possible. Super Pixels are another matter entirely, and not fully implemented yet even in A2B’s Image Tone Rendering which produces entirely different output. Super Pixels have nothing at all to do with this yet. Suffice to say you are looking at something new for A2B that is somewhat more based on the work that I did last year with Jonas Grönhagen and his own work with the Simplifly II online SHR converter.

A2B works directly with 24-bit color but a modern continuous tone truecolor image must be converted to a GIF file (or equivalent) to be used with Convert3200.

The A2B converter generally does a better job converting a good quality 24-bit truecolor image to SHR, but even an old GIF file can be saved as a BMP file and converted using A2B with or without dithering. New GIFs are better (today our graphics toolsets are better and like the A2B converter, conform to standard color spaces like Rec. 709 or sRGB), but even new GIFs are still not nearly as accurate as a 24-bit continuous tone truecolor image.

Some of A2B’s 200 palette SHR output from 24-bit input (including some of the output in this article) already has more unique IIgs colors than a 256 color GIF file can hold. As previously noted, further development of “full palette conversion” for A2B, expected to be completed before 2016, will likely result in improved 200 palette output with (I hope) thousands of unique IIgs colors, and improved 16 palette output with up to all 256 colors unique and all 256 colors used, and smoother dithering, with more detail in both dithered and non-dithered output.

Color Counts

The comparisons in this article include color counts provided by The GIMP 2.8 that are pretty self explanatory. A2B conversion provides 2 counts because A2B works with 24-bit truecolor palettes for full precision and converts them to 12-bit IIgs palettes when writing SHR output to disk. This generally results in duplicate IIgs colors and much fewer unique IIgs colors than the real 24-bit colors that were in the conversion palette. Full palette conversion enhancements discussed above are expected to eliminate the dupes and result in much greater detail and many more colors.

Converted GIF File Comparison – Girl256

The input image used below for the first comparison started as a 255 color GIF file from the Convert3200 webpage. It was converted to a 24-bit BMP to avoid color loss during editing, and for aesthetics, the “garbage” on the bottom left was cleaned-up with pure white, but no other changes were made. The edited 24-bit file was then converted back to GIF again for Convert3200, with 256 unique 24-bit colors. This was not necessary for A2B since A2B works directly with 24-bit color BMP input files.

Dithered Output – A2B Only

Input Image – 320 x 200 x 256 colors

A2B – 1 palette dithered – 15 unique colors

A2B – 16 palettes dithered – 83 unique IIgs colors (229 unique 24-bit colors)

A2B – 200 palettes dithered – 183 unique IIgs colors (1073 unique 24-bit colors)

Non-Dithered Output – Convert3200 and A2B

Convert3200 – 1 palette non-dithered – 16 unique IIgs colors

A2B – 1 palette non-dithered – 15 unique IIgs colors (16 unique 24-bit colors)

Convert3200 – 16 palettes non-dithered – 95 unique IIgs colors

A2B – 16 palettes non-dithered – 86 unique IIgs colors (244 unique 24-bit colors)

Convert3200 – 200 palettes non-dithered – 147 unique IIgs colors

A2B – 200 palettes non-dithered – 227 unique IIgs colors (2089 unique 24-bit colors)

.The input images used for the rest of the comparisons in this article are modern 24-bit continuous tone truecolor images.

Converted 24-bit Input File Comparison – RAM

Input Image – 320 x 200 x 45808 unique 24-bit colors (256 unique GIF colors)

A2B – 1 palette dithered – 16 unique colors

A2B – 16 palettes dithered – 98 unique IIgs colors (237 unique 24-bit colors)

A2B – 200 palettes dithered – 204 unique IIgs colors (1258 unique 24-bit colors)

Non-Dithered Output – Convert3200 and A2B

Convert3200 – 1 palette non-dithered – 16 unique IIgs colors

A2B – 1 palette non-dithered – 16 unique colors

Convert3200 – 16 palettes non-dithered – 105 unique IIgs colors

A2B – 16 palettes non-dithered – 100 unique IIgs colors (252 unique 24-bit colors)

Convert3200 – 200 palettes non-dithered – 187 unique IIgs colors

A2B – 200 palettes non-dithered – 243 unique IIgs colors (2835 unique 24-bit colors)

Converted 24-bit Input File Comparison – SUNDOWN

Input Image – 320 x 200 x 45699 unique 24-bit colors (256 unique GIF colors)

A2B – 1 palette dithered – 16 colors

A2B – 16 palettes dithered – 148 unique IIgs colors (222 unique 24-bit colors)

A2B – 200 palettes dithered – 370 unique IIgs colors (1265 unique 24-bit colors)

Non-Dithered Output – Convert3200 and A2B

Convert3200 – 1 palette non-dithered – 16 unique IIgs colors

A2B – 1 palette non-dithered – 16 unique colors

Convert3200 – 16 palettes non-dithered – 147 unique IIgs colors

A2B – 16 palettes non-dithered – 153 unique IIgs colors (238 unique 24-bit colors)

Convert3200 – 200 palettes non-dithered – 231 unique IIgs colors

A2B – 200 palettes non-dithered – 468 unique IIgs colors (2602 unique 24-bit colors)

Converted 24-bit Input File Comparison – TETONS

This Image of the Moulton Barn below (quite widely used on Wikipedia) started life on the Canon EOS D60, a DLSR that works within the sRGB color space which uses the Rec. 709 primaries, and was scaled to 320 x 200 using ImageMagick which uses the Rec. 709 color space (all the input files in this article were converted and scaled in ImageMagick using the Rec. 709 color space). A2B converted this (and all the other SHR files in this article) using the Rec. 709 color space. A2B works directly with 24-bit color but since a modern continuous tone image must be converted to a GIF file to be used with Convert3200, all the GIF files used by Convert3200 to provide the conversions in this article were created by ImageMagick using the Rec. 709 color space.

Input Image – 320 x 200 x 37349 unique 24-bit colors (256 unique GIF colors)

A2B – 1 palette dithered – 16 unique colors

A2B – 16 palettes dithered – 118 unique IIgs colors (234 unique 24-bit colors)

A2B – 200 palettes dithered – 258 unique IIgs colors (1237 unique 24-bit colors)

Non-Dithered Output – Convert3200 and A2B

Convert3200 – 1 palette non-dithered – 16 unique IIgs colors

A2B – 1 palette non-dithered – 16 unique colors

Convert3200 – 16 palettes non-dithered – 130 unique IIgs colors

A2B – 16 palettes non-dithered – 119 unique IIgs colors (235 unique 24-bit colors)

Convert3200 – 200 palettes non-dithered – 191 unique IIgs colors

A2B – 200 palettes non-dithered – 292 unique IIgs colors (2274 unique 24-bit colors)

Downloads and Closing Remarks

Summer of 2015 Download Link

The A2B Current Snapshot (pre-release of Version 7.0) used to produce this article, and other articles, accompanying disks and samples can be downloaded at the following link:

http://www.appleoldies.ca/a2b/Summer2015/

A2B comes with source and for Windows users, a Win32 binary and should compile in a gcc compatible system including OSX and Linux. It is written in ANSI C with no dependencies on 3^rd party libraries.

Files for this Article

The input and output files used in this article can also be downloaded in zip format from the link above. The output files in the zip file are in both Apple IIgs format and Magnified png format

Sample Slideshows (Thousands of SHR files)

Also available from the link above, for review purposes, are 7-disk images in 20MG hdv format containing thousands of samples of dithered and non-dithered A2B 16-palette and 200-palette output created by A2B using the current external segmented palette output option. These disk images are organized into slideshows and will run on a IIgs or a IIgs emulator like kegs32. The quality of the output varies and is completely “unretouched” in order to provide an unvarnished overview of the current status of A2B’s output using a variety of continuous tone content. Some conversion are good, some are bad, and some are ugly. Regardless, these are some of the actual test images used in A2B’s latest development.

Additional Sample Files

During the development of A2B between June and July 2015, A2B produced hundreds of thousands (likely over a million) SHR files of a similar nature to the subset provided on these disk images. It is simply impractical and far too time consuming to make all A2B’s test output available from the appleoldies.ca website, and just as impractical and time consuming to provide input files and other development artifacts online. The Internet is filled with images that you can convert with A2B so that is no hardship.

Additional Development and Downloads

I will be selectively providing additional documents using A2B to produce SHR output and also about additional development for the Summer of 2015, with supporting downloads in the days ahead. All this will be at the link above, including A2B’s latest snapshot including source code.

Conclusions About This Article

A2B converts to all the Apple IIe graphics modes with the exception of HGR which is handled by Bmp2DHR. A2B is also part of the Bmp2DHR toolset and performs many other tasks. It is an experimental open source utility free for all to use and runs on most modern computers. For SHR output it is a mode320 and mode3200 screen conversion utility. It is really a simple program, and its development is easy for me, but its use is at a very expert level for the “uniniated”. It also assumes the presense of knowledge of all things modern and graphic and has many contributors of ideas and was not built in a vacuum, but is not a commercial product either.

Convert3200 is actively used in the retro-computing community. It was in its time a first class commercial product for a trailing edge computer that a retro-programmer like me can’t help but love. I never looked at Convert3200’s documentation much or its code when I started writing SHR converters, but its pretty obvious looking back over the last couple of years that the people who gave me ideas are intimately familiar with Convert3200 and many other graphics converters. So it is not by coincidence that my thinking in A2B is heavily influenced not only by some very great graphics experts like John Bridges but by Antoine Vignau. To say that Antoine and a handful of other people taught me almost everything that I know about SHR would not have been far from the truth for the first year or so that I mucked with SHR.

Convert3200 is a commercial product and has its place in history and has many different useful features from A2B. As far as I am concerned, A2B is making its own history in its goal to provide a sandbox to develop the best all-around Apple II graphics editor in history. In the meantime as far as I am concerned SuperConvert is no match for Convert3200 when it comes to Mode320 color conversions. I can’t even get Prism to open a GIF file, so who knows what Prism will do? It does nothing for me. Convert3200 provides me with a benchmark. To me, it is the “Gold Standard” for IIgs graphics converters of the era.

A2B has all sorts of other programs to help it along so let’s not compare the two programs, let’s recognize the limitations of the output of each, the similarities and the differences between them, why a GIF file conversion can’t give us the truecolor that we need to go further, and things of that nature. As far as comparing my retro-programming to Antoine’s, we can’t do that. I am an average IBM-PC C programmer who knows 8088 assembly much better than 6502 assembly, and Antoine is a IIgs assembly language game developer of historical proportions through and through. I have a pretty good handle on modern graphics and this SHR stuff though, but I have yet to even write a Mode3200 screen loader, something I am sure that even back then Antoine and many others could do without a thought. Maybe next year.

All the Best,

Bill Buckels

bbuckels@mts.net

July 24, 2015