BitPast - Apple II Graphics Converter

BitPast is a modern, native macOS application for converting images into authentic Apple II and Apple IIgs graphic formats.

✨ Features

🖥️ Modern macOS Interface

• Drag & Drop: Drag multiple images directly from Finder or the web.
• Batch Processing: Load dozens of images into a grid browser and process them one by one.
• Live Preview: See changes instantly as you adjust sliders for dithering, crosshatch, or color bleed.
• Zoom & Pan: Inspect every single pixel with a high-performance zoomable preview.

🎨 Powerful Conversion Engines

🍏 Apple II (8-Bit)

Powered by b2d, supporting the full range of classic graphics modes:

• DHGR (Double Hi-Res): 140x192 (16 colors) or 560x192 (Monochrome).
• HGR (Hi-Res): 280x192 (6 colors).
• LGR / DLGR: Lo-Res and Double Lo-Res block graphics.
• Color & Monochrome: Fully supported with optimized rendering.

🌈 Apple IIgs (16-Bit)

Powered by a native Swift engine featuring advanced color quantization:

• 3200 Mode (Smart Scanlines): Uses Median Cut Quantization and intelligent scanline clustering to utilize all 16 palettes simultaneously. This allows for near-photorealistic images by dynamically assigning specific palettes to different vertical sections of the image.
• Standard Modes: 320x200 (16 colors) and 640x200 (4 colors).
• Color Accuracy: Full utilization of the Apple IIgs 12-bit RGB color space (4096 colors).

🎛️ Fine-Tuning Control

General:

• Dithering Algorithms: Floyd-Steinberg, Atkinson, Jarvis-Judice-Ninke, Stucki, Burkes, and Ordered (Bayer 4x4).
• Smart Scaling: Automatically maps input resolutions (like 640x480 VGA) to safe resolutions to prevent artifacts.

Apple II Specific:

• Crosshatch Threshold: Simulate monitor scanline effects.
• Color Bleed Reduction: Clean up NTSC artifacts for sharper images.
• Palettes: Over 15 historic palettes (Standard, NTSC simulation, RGB, Greyscale, etc.).

Apple IIgs Specific:

• Merge Tolerance: Controls how aggressively scanlines are clustered in 3200 mode.
• Saturation Boost: Compensates for the limited 4-bit color depth to make images "pop".
• Gamma Correction: Adjust brightness distribution for retro CRTs.

💾 Export Formats

• Modern Previews: Export as PNG, JPG, GIF, or TIFF for web use.
• Native Binaries: - Apple II: .BIN (binary dumps) ready for hardware.
  • Apple IIgs: .SHR (Super Hi-Res, Type $C1) compatible with GS Paint and generic loaders.
• ProDOS Disk Images: Create bootable .PO, .2MG, or .HDV disk images directly from the app (requires cadius).

🚀 How to Use

1. Drag Images into the left "Image Browser" panel.
2. Select an image to preview it.
3. Choose your System (Apple II or Apple IIgs).
4. Tweak the Mode, Dither, and Sliders until the Live Preview looks perfect.
5. Click Export in the bottom right corner.
   • Choose PNG/JPG for a visual preview.
   • Choose Native Format to save the raw file (.BIN / .SHR).
   • Choose Create ProDOS Disk to package the file onto a disk image.

🛠️ Technical Details

BitPast is built with Swift and SwiftUI for macOS.

• Frontend: SwiftUI (Grid Views, HSplitView, Combine for debounced live previews).
• Backend (Apple II): b2d (modified build with struct packing fixes for modern macOS ARM64/x86_64 architecture).
• Backend (Apple IIgs): Native Swift implementation using Median Cut algorithm and Euclidean distance scanline clustering.
• Disk Operations: Integrated wrapper for cadius (by BrutalDeluxe) to manage ProDOS volumes.

📦 Installation

From Source

1. Clone the repository.
2. Open BitPast.xcodeproj in Xcode.
3. Ensure the b2d and cadius binaries are present in the project bundle resources.
4. Build and Run (Requires macOS 12.0+).

From Binary Release

Since this app is not distributed through the official Apple App Store and may not have been notarized by a paid Apple Developer Account, macOS might display a security warning upon the first launch.

You may see a message stating: "The app cannot be opened because it is from an unverified developer."

How to bypass this warning (one-time process):

Close the warning window. Go to the app in Finder (e.g., in your Applications Folder). Hold the Control key and click on the app icon (or use the Right-Click menu). Select Open from the context menu. In the subsequent dialog box, confirm that you want to open the app by clicking Open again. The application will now launch and will be trusted by macOS for all future starts. If this does not work then

1. Open Terminal You can find it in: Applications → Utilities → Terminal
2. Run the following command (in case you installed it in the Applications directory):
   xattr -cr /Applications/BitPast.app

👏 Credits

• Bill Buckels: For creating the original b2d (Bmp2DHR) command-line tool. Visit AppleOldies.ca.
• Brutal Deluxe: For the Cadius tool used for ProDOS disk management.Visit https://www.brutaldeluxe.fr/

📄 License

This project is open source. The UI code is provided under the MIT License. The bundled b2d binary follows the original license by Bill Buckels (Royalty-free use/modification allowed).