Try a conversion

These are real results from MegaconvertGS, made in an emulated IIgs. Pick a picture, then a conversion.

Picture

Conversion

What it does

Open nearly 70 formats from a dozen kinds of computer, chosen in the Load formats window or recognised by File > Open.
Remap to 320 x 200 in 16 colours, 640 x 200 in 4, 640 dither mode or multipalette, with SuperConvert's palettes, dithering and error diffusion.
Filter true colour pictures: equalize, median, sigma, emboss, blur, sharpen, solarize, find edges, contrast, rotate and flip.
Monochrome with error diffusion, pattern dither, threshold or halftone, and back again.
Batch many files or whole folders with Load & convert, saved automatically if you like.
Save as Apple Preferred, $C1, PackBytes, PaintWorks, Finder icons, icon resources, a desktop picture, GIF, PNG, TIFF and BMP, and New Apple II HiRes and Double HiRes screens (colour or black & white, plain or packed) and LoRes and Double LoRes screens, dithered in the Apple II colours, with a choice of error diffusion, pattern or no dithering, filling the screen or keeping the picture's proportions.
Babelfish with Seven Hills' freeware Babelfish installed, imports and exports go through its translators and its own Open and Export dialogs, as in SuperConvert 4: PixelMaps and true colour pictures in and out (Apple Preferred, Super Hi-Res, MacPaint, Print Shop, GEM/IMG, PPM and more).

Load formats

The computer types of the Load formats window. New marks formats SuperConvert didn't have.

Apple II family

HiRes and Double HiRes (New also packed, type $08 and LZ4FH; Double HiRes as .BIN + .AUX pairs, Dazzle Draw / A2FC and bmp2dhr pieces), New LoRes and Double LoRes, Print Shop graphics, ThunderScan scans, Works of Art pages, TDM text screens

Apple IIgs

Super Hi-Res ($C0, $C1, Apple Preferred, New whole when larger than a screen or with 3200 colors), PaintWorks, Paintworks Gold, DreamGrafix, "3200 color", Print Shop IIgs, Finder icons, AST and ComputerEyes

Atari ST

Degas, Degas Elite, Neochrome, Tiny, Spectrum 512

Amiga

IFF ILBM with HAM, Extra HalfBrite and 24-bit

Commodore 64

Doodle, Koala, Print Shop and other hires bitmaps, New Art Studio and Interpaint hires, New Advanced Art Studio, New FLI Graph, New Amica Paint

Macintosh

MacPaint, ScreenMaker, New QuickDraw PICT

PC

BMP, PC Paintbrush, GEM/Ventura IMG, DeluxePaint LBM, FliAway frames

Unix

Sun Rasterfile, SGI, PBM, PGM, PPM

New Amstrad CPC

Screens in mode 0, 1 and 2, with or without the AMSDOS header or packed by OCP Art Studio, in the colours and mode of their .PAL file

New Atari 8-bit

MicroPainter, Graphics 8 and Graphics 9 screens

New MSX

Screen 2, 5, 7 and 8, with the file's palette

New ZX Spectrum

Screens (.SCR), in the Spectrum's 15 colours

Any computer

JPEG (also New progressive), PNG, GIF, CompuServe RLE, IPI, QRT, New TIFF, New Targa

External (Babelfish™)

True Color and PixelMap imports through Babelfish's translators, when Babelfish is installed

Speed

Made several times faster without changing a single result. Seconds on a 2.8 MHz IIgs (emulated):

Remap a 640 mode screen to 320 mode

95.5 → 10.9 s 8.8x

Remap a picture to 640 mode

54.4 → 9.9 s 5.5x

The remap test suite (43 remaps)

1585 → 387 s 4.1x

Monochrome image back to a screen

75.3 → 19.8 s 3.8x

Open a 700 x 500 PNG

177 → 64 s 2.8x

Open a 320 x 200 JPEG

41.0 → 18.1 s 2.3x

Save as PNG

62.0 → 27.6 s 2.2x

Open a 640 x 480 JPEG photo

127.3 → 73.9 s 1.7x

Remap a 700 x 500 picture

26.7 → 16.4 s 1.6x

The median filter

30.3 → 18.4 s 1.6x

The sigma filter

16.0 → 10.1 s 1.6x

The blur filter

19.6 → 13.9 s 1.4x

before now

On the desktop

The Load formats and Save formats windows, with the Macintosh formats listed — Load formats and Save formats, as in SuperConvert

The Remap dialog with the graphic mode, palette, rendering and size — The Remap dialog: mode, palette, rendering, size

A picture in the image window beside the format windows — A picture in the image window

Download

MegaconvertGS.po is an 800K ProDOS disk with the program, its help text, its title picture and its Finder icon. Free and open source.

Boot GS/OS (tested with System 6.0.4).
Open the MegaconvertGS disk and double-click MegaconvertGS.
To keep it on a hard disk, copy MegaconvertGS, MCGS.Help and MCGS.Title into one folder, and MCGS.Icons into the disk's Icons folder.

On a real IIgs, write the image to a 3.5" disk or use a FloppyEmu or BlueSCSI. In MAME (on a Mac, easiest through Ample), boot your System 6 disk and put the image in a 3.5" drive.

Download from GitHub User manual (PDF, 39 pages) Source code