BitPast

About BitPast

BitPast is a modern, native macOS application for converting images into authentic retro computer graphic formats. Supporting 15 classic systems including Apple II, Apple IIgs, BBC Micro, Commodore 64, VIC-20, ZX Spectrum, Amstrad CPC, Plus/4, Atari 800, Atari ST, Amiga 500, Amiga 1200, IBM PC, MSX, and TRS-80 Color Computer - each with their authentic color palettes, resolutions, and native file formats.

Key Features

Everything you need to create authentic retro graphics

🖥️

Modern macOS Interface

Drag & drop multiple images directly from Finder or the web. Batch processing with grid browser and live preview with real-time adjustments.

🎮

15 Retro Systems

Apple II, Apple IIgs, Amiga 500/1200, Amstrad CPC, Atari 800, Atari ST, BBC Micro, C64, MSX, PC (CGA/EGA/VGA), Plus/4, TRS-80 CoCo, VIC-20, and ZX Spectrum.

🔍

Zoom & Pan

Inspect every single pixel with a high-performance zoomable preview and real-time rendering.

⚙️

Fine-Tuning Control

15+ dithering algorithms, contrast enhancement (HE, CLAHE, SWAHE), color matching modes, saturation and gamma controls.

🌈

Advanced Color Modes

Apple IIgs 3200 colors, Amiga HAM6/HAM8 modes, VGA 256 colors, and intelligent palette optimization for all systems.

💾

Native File Formats

Export to authentic formats: .SHR, .IFF, .PCX, .SCR, .PI1, .ART, .KLA, .PRG, and more. Create bootable ProDOS disk images.

Supported Systems

Convert images for all major retro platforms

🍏 Apple Computers

Apple II DHGR, HGR, LGR modes .BIN output

Apple IIgs 3200 colors, 320/640 modes .SHR, .3200 output

🐚 Commodore Computers

Commodore 64 HiRes & Multicolor .ART, .KLA output

VIC-20 HiRes & LowRes .PRG output

Plus/4 HiRes & Multicolor .PRG output

Amiga 500 OCS/ECS, HAM6 .IFF output

Amiga 1200 AGA, HAM8 .IFF output

🖥️ Other Systems

Atari ST 320x200, 16 from 512 colors .PI1 (DEGAS) output

ZX Spectrum 256x192, attribute cells .SCR output

Amstrad CPC Mode 0 & Mode 1 .SCR output

IBM PC CGA, EGA, VGA, Text modes .PCX, .ANS output

MSX / MSX2 Screen 2, 5, 8 .SC2, .SC5, .SC8 output

Atari 800 Graphics 8, 9, 10, 11, 15 .GR8, .GR9, etc. output

BBC Micro Mode 0, 1, 2, 4, 5 .BBC output

TRS-80 CoCo PMODE 1-4, CoCo 3 .BIN, .CM3 output

💾 Export Formats

Modern Preview PNG, JPG, GIF, TIFF For web use

Native Binaries 20+ authentic formats Ready for emulators

💿 Virtual Disk Images

Create disk images for ALL supported retro systems

Apple II / IIgs .PO, .2MG, .HDV 140KB, 800KB, 32MB

Commodore 64/VIC-20/Plus4 .D64, .D71, .D81 170KB, 340KB, 800KB

Amiga 500 / 1200 .ADF 880KB, 1.76MB

Atari 800 .ATR 90KB, 130KB, 180KB, 360KB

Atari ST .ST 360KB, 720KB, 1.44MB

BBC Micro .SSD, .DSD 100KB, 200KB, 400KB

MSX .DSK 360KB, 720KB

Amstrad CPC .DSK 180KB, 360KB

ZX Spectrum .TRD, .DSK 640KB, 180KB

IBM PC .IMG 360KB, 720KB, 1.2MB, 1.44MB

TRS-80 CoCo .DSK 180KB, 360KB

Screenshots

See the app in action

Apple IIgs 3200 Color Mode

Near-photorealistic results using all 16 palettes simultaneously. Smart scanline clustering and Median Cut Quantization deliver stunning quality.

Apple IIgs with GS/OS Theme

Convert modern images to authentic Apple IIgs 3200-color format. The classic GS/OS-inspired interface brings nostalgia while delivering professional results.

Apple II with Green Phosphor Theme

Experience the classic green monitor aesthetic. Convert images to Double Hi-Res format with authentic dithering and real-time preview.

Commodore 64 with Blue Theme

The iconic C64 blue interface. Convert images to HiRes or Multicolor mode with accurate VICE/Pepto palette and multiple dithering options.

Advanced Palette Editor

Fine-tune your conversions with the built-in palette editor. Edit individual scanline palettes for Apple IIgs 3200-color mode with full undo/redo support.

Technical Details

BitPast is built with Swift and SwiftUI for macOS. Each retro system has its own dedicated converter with authentic color palettes, resolution handling, and native file format output. Advanced features include K-D tree optimized color matching, median-cut palette quantization, HAM (Hold-And-Modify) encoding for Amiga, attribute-based conversion for ZX Spectrum, and interleaved bitplane encoding for authentic file formats.