c8acdca86b
- Document all new CLI parameters (--relax, auto-output) - Add smart defaults section (yrow=8, auto-generated filenames) - Include usage examples for relax feature - Document output organization (results/ vs results/debug/) - Add PowerShell batch command example from debug mode - Update parameter descriptions with current behavior Also: Set --relax default to 100 when flag used without value
93 lines
3.5 KiB
Markdown
93 lines
3.5 KiB
Markdown
# Strip Photography / Slit Photography
|
|
|
|
A digital implementation of **strip photography** (also called **slit photography**) that captures a two-dimensional image as a sequence of one-dimensional images over time.
|
|
|
|
|
|
|
|
Strip photography records a moving scene over time by extracting the same line position from each video frame and assembling them into a composite image where:
|
|
- One axis represents **space** (the slit/line being observed)
|
|
- The other axis represents **time** (progression through video frames)
|
|
- Moving objects appear as visible shapes, stationary objects as stripes
|
|
- Object width is inversely proportional to speed (faster = narrower, slower = wider)
|
|
|
|
## Usage
|
|
|
|
**Basic Usage** - Uses smart defaults (yrow=8, auto output to results/):
|
|
```bash
|
|
uv run main.py .\line500fps32pix.mp4
|
|
```
|
|
Output: `results/line500fps32pix_a3f2_t0_01.jpg` (auto-generated with UUID and threshold)
|
|
|
|
**Row Mode** - Extract horizontal lines with custom settings:
|
|
```bash
|
|
uv run main.py .\line500fps32pix.mp4 --yrow 16 --threshold 0.005
|
|
```
|
|
|
|
**With Relax** - Include extra frames around threshold frames for smoother transitions:
|
|
```bash
|
|
uv run main.py .\line500fps32pix.mp4 --relax 5
|
|
# or use default relax value (100):
|
|
uv run main.py .\line500fps32pix.mp4 --relax
|
|
```
|
|
|
|
**Debug Mode** - Analyze changes and generate threshold recommendations:
|
|
```bash
|
|
uv run main.py .\line500fps32pix.mp4 --debug
|
|
```
|
|
Output: `results/debug/line500fps32pix_7c91_t0_01_changes.png`
|
|
|
|
|
|
Debug mode generates PowerShell commands to test all suggested thresholds:
|
|
```powershell
|
|
0.0087,0.0098,0.0112,0.0121,0.0159 | %{uv run .\main.py video.mp4 --threshold $_}
|
|
```
|
|
|
|
## Setup
|
|
Install dependencies with uv:
|
|
```bash
|
|
uv sync
|
|
```
|
|
|
|
## Parameters
|
|
|
|
### Required
|
|
- `video_file` - Path to input video file
|
|
|
|
### Optional
|
|
- `--xcolumn N` - Extract vertical line at x-coordinate (column mode)
|
|
- `--yrow N` - Extract horizontal line at y-coordinate (row mode, **default: 8**)
|
|
- `--output PATH` - Output file path (default: auto-generated to `results/` with UUID)
|
|
- `--threshold N` - Change threshold 0-1 for frame inclusion (default: 0.01)
|
|
- `--relax [N]` - Include N extra frames before/after threshold frames (default: 0, or 100 if flag used without value)
|
|
- `--debug` - Analyze changes without creating strip image, outputs to `results/debug/`
|
|
|
|
### Output Modes
|
|
- **Column mode**: Extracts vertical line (`--xcolumn`) → Width = frames, Height = video height
|
|
- **Row mode**: Extracts horizontal line (`--yrow`, **default**) → Rotated 90° CW for proper orientation
|
|
|
|
## Features
|
|
|
|
**Smart Defaults**:
|
|
- Defaults to row mode at y=8 if no mode specified
|
|
- Auto-generates output filename with UUID and threshold: `results/video_a3f2_t0_01.jpg`
|
|
- Automatically appends `.jpg` extension if none provided
|
|
- Row mode output is rotated 90° clockwise for proper viewing
|
|
|
|
**Change Detection**: Automatically filters frames with minimal changes using configurable thresholds
|
|
- Use `--threshold` (0-1) to control sensitivity
|
|
- `--debug` mode provides threshold recommendations and change analysis
|
|
- Higher thresholds = more compression, fewer frames
|
|
|
|
**Relax Feature**: Include extra frames around significant changes for smoother transitions
|
|
- `--relax 5` includes 5 frames before/after each threshold frame
|
|
- `--relax` without value defaults to 100 frames
|
|
|
|
**Threshold Guide**:
|
|
- `0.001-0.005`: High sensitivity (10-30% compression)
|
|
- `0.005-0.02`: Medium sensitivity (30-70% compression)
|
|
- `0.02+`: Low sensitivity (70%+ compression)
|
|
|
|
**Output Organization**:
|
|
- Normal mode: `results/` folder
|
|
- Debug mode: `results/debug/` folder
|