ai-game-2/.opencode/skills/alpha-mask-creator/SKILL.md

name, description

name	description
alpha-mask-creator	Takes an image and creates a high quality alpha mask of the requested entity. Typically invoked when the user asks to "create a specific alpha mask for"

Alpha Mask Creator

This skill creates alpha masks from images based on user requests. Use this when the user asks to "create a specific alpha mask for..." along with providing an image.

Workflow

0. Extract layer (conditional)

If the user provided a layer name from an ora file, you should use the ora-editing skill to extract a png of that layer. First use the inspect to list the layers, then use the extract.

1. Draw Polygon Outline (optional, default)

Use the polygon-drawer skill to draw a polygon outline around the identified object. If the user asks to bypass the polygon, do so. Save the output to ./tmp/ with a sensible filename:

• Format: <original_name>.<object>.png
• Example: If the user wants a door mask from room_010.png, name it room_010.door.png

2. Extract Mask

Run the extract_mask script to generate the alpha mask. If a polygon was added, make sure to include "with the outline", or "outlined in ". You can also explicitly omit things:

source ./tools/venv/bin/activate
python tools/extract_mask.py "the door with the red outline" ./tmp/<original_name>.<object>.png ./tmp/<original_name>.<object>.mask.png

Examples:

• The boulder outlined in red
• The door with the blue polygon around it
• The fence, excluding the bushes behind it
• The house, including the windows and chimney, outlined in blue
• The mailbox, including the flag, omitting the house behind it

3. Quality Check

Examine the generated mask using the image-expert agent:

• Check if the mask is precise and accurate
• Verify the object is properly isolated
• Ensure no artifacts or incorrect areas

If the mask quality is poor:

• Retry the polygon-drawer step with different parameters or seed
• Iterate until the mask is satisfactory

5. Report Results

Tell the user:

• Location of the polygon outline image: ./tmp/<original_name>.<object>.png
• Location of the mask: ./tmp/<original_name>.<object>.mask.png
• Confirm the mask quality is acceptable

6. Integrate into existing ora file

If the user asked to create an alpha mask for a layer from an ora file, offer to add the masked element to the ora file, using the ora-editing skill.

Naming Conventions

User Request	Original File	Output Files
Door	room_010.png	room_010.door.png, room_010.door.mask.png
Tree	forest_bg.png	forest_bg.tree.png, forest_bg.tree.mask.png
Character	scene_005.png	scene_005.character.png, scene_005.character.mask.png

Tools Used

• image-inspector - Analyze images to locate objects
• polygon-drawer - Draw polygon outlines
• bash - Run extract_mask script
• image-expert - Verify mask quality

Example Interaction

User: "Create a specific alpha mask for the door in this image" [attaches cottage_exterior.png]

You:

1. Analyze the image to locate the door
2. Draw polygon around the door → ./tmp/cottage_exterior.door.png
3. Extract mask → ./tmp/cottage_exterior.door.mask.png
4. Verify mask quality
5. Report: "Mask created successfully! Files saved to:
   • Polygon outline: ./tmp/cottage_exterior.door.png
   • Alpha mask: ./tmp/cottage_exterior.door.mask.png"