ConvertDualHGR — dual-page compositor with WebGL 120 Hz preview

Conversion controls

Image preparation

Fit source

Drop a photograph anywhere on this tool, or open a local image. Conversion uses the 280 × 192 source canvas.

Live camera capture

Capture limit10 fps

Camera stopped.

Start camera to capture frames continuously and convert each latest available frame in a Web Worker. Capture may run faster than HGR optimization; intermediate frames are intentionally dropped. Use Fast search quality for higher throughput. Camera capture converts automatically even if Auto-convert is unchecked.

Optimization

Processing backend

The same 7-pixel byte-pair search and spatial dithering algorithm runs as compiled native WebAssembly or JavaScript. WASM is the default; if unavailable, the tool reports the issue and falls back to JavaScript. The WebGL animation remains independent of the conversion worker.

Search quality

HGR / HGR2 duty cycle

Composite color model

Ordered dither strength5

Error diffusion80%

Luminance emphasis1.6×

Color-switch penalty0.006

The color-switch penalty discourages widely different page colors in the optimizer.

Preview & updates

Animate HGR/HGR2 page flipping

Page-flip frame rate60 Hz

Preview renderer idle. Supports up to 120 Hz where browser and monitor permit.

WebGL alternates three HGR frames per HGR2 frame at 75/25, or one of each at 50/50. The clock stays active while new camera conversions replace both page textures atomically. The selected 10–120 Hz flip rate is limited by the actual display/browser refresh; WebGL cannot force a 60 Hz monitor to show 120 distinct frames.

Auto-convert after changing a control

Optimization changes and new still images automatically restart conversion after a short debounce. Live camera capture continuously converts the newest frame independently of this checkbox. Animation controls do not require reconversion.

Output files

Each binary image is 8,192 bytes in native Apple II scanline memory layout. The combined download contains the HGR page followed by HGR2.

Verification

Combined output — 75% HGR + 25% HGR2

Static composite

Static bitmap decoded from both exported HGR pages. Enable animation to compare actual page flipping against the averaged preview.

Demo source is being prepared.

Conversion results

RGB error (RMSE): —
YUV objective / px: —
Convert time: —
Processing: —
Output pages: 2 × 8 KB

Pixel inspector

Move the pointer over the combined image to inspect decoded colors from both pages.

X/Y: — Source: — HGR / HGR2: — Composite: — Bytes: —

Source image / live camera

280 × 192

HGR

75% duty / $2000

HGR2

25% duty / $4000

Interpretation

The core optimizer runs in WebAssembly by default (with a JavaScript alternative) and chooses two legal HGR byte streams jointly for the selected duty cycle. Each pixel's displayed color is decoded from its own byte phase bit and neighboring pixel bits, including transitions between bytes. The static preview and PNG use the weighted mix duty × HGR_RGB + (1 − duty) × HGR2_RGB by default, reconstructed from the actual exported HGR bytes.

WebGL displays a repeating 3:1 sequence at 75/25 or 1:1 at 50/50, with two pairs of GPU textures so newly converted camera frames replace both pages on a single animation callback. This is a display-rate preview, not a raster/Vaporlock hardware emulator. A browser or display below 120 Hz cannot present 120 unique frames per second; the preview adapts to the measured refresh rate and reports its achieved rate. The static PNG export always uses the selected duty ratio.