sprite-segment-3x3grid

Imported from unity-technologies/skills (skills/sprite-segment-3x3grid/SKILL.md) via skills.sh. Install upstream with npx skills add unity-technologies/skills --skill sprite-segment-3x3grid. Copyright stays with the author.

Sprite Color Grid Analysis

Purpose

This skill analyzes Sprite textures by segmenting them into a 3x3 grid and outputting a text representation based on color matching with the center cell.

Parameters

Match Threshold

The match threshold determines what percentage of pixels in a non-center cell must match the center's majority color for that cell to be considered a "match" (.).

Default: 75%

Algorithm

1. Segment the Sprite: Divide the Sprite's texture region into a 3x3 grid (9 cells total)
2. Identify Center Color: Calculate the majority (most frequent) color in the center cell (position [1,1])
3. Compare Each Cell: For each of the 8 surrounding cells, calculate what percentage of pixels match the center's majority color. If the percentage meets or exceeds the match threshold, the cell is a match (.); otherwise it is not (X)
4. Generate Output: Create a text representation using the legend below

Output Legend

Output Format

The output is a single line with three groups of three characters, separated by /. Each group represents one row of the grid.

Order: Top to Bottom rows, Left to Right within each row.

Format: [TopRow] / [MiddleRow] / [BottomRow]

Each row contains 3 characters separated by spaces: [Left] [Center] [Right]

Grid Position Mapping

Grid Layout:        Output Order:
[0,0] [1,0] [2,0]   1  2  3   -> First group
[0,1] [1,1] [2,1]   4  5  6   -> Second group (5 is always *)
[0,2] [1,2] [2,2]   7  8  9   -> Third group

Examples

Example 1: Center matches top-left and bottom-right only

. X X / X * X / X X .

Grid interpretation:

.  X  X
X  *  X
X  X  .

Example 2: Center matches all surrounding cells

. . . / . * . / . . .

Example 3: Center matches none of the surrounding cells

X X X / X * X / X X X

Example 4: Center matches bottom row only

X X X / X * X / . . .

Implementation Guidance

Calculating Center's Majority Color

For the center cell:

1. Sample all pixels within the cell's bounds
2. Group pixels by color (consider using a color tolerance threshold for similar colors)
3. The majority color is the color with the highest pixel count
4. For tie-breaking, use the first color encountered

Matching Non-Center Cells

For each of the 8 surrounding cells:

1. Count the total number of pixels in the cell
2. Count how many pixels match the center's majority color (using color tolerance)
3. Calculate the match percentage: matchingPixels / totalPixels
4. If match percentage >= threshold, cell is a match (.); otherwise (X)

Color Tolerance

When comparing pixel colors:

• Consider using a tolerance threshold (e.g., RGB distance < 10) for "matching"
• Alternatively, for sprites with limited palettes, exact matching may be appropriate
• Account for alpha channel if relevant to the use case

Sprite Bounds

Use the Sprite's rect property to determine the pixel region to analyze:

• sprite.rect.x, sprite.rect.y for the origin
• sprite.rect.width, sprite.rect.height for dimensions
• Divide width and height by 3 to get cell dimensions

References

Code Template: "scripts/SpriteGridAnalysis.cs"

Use Cases

• Documentation: Describe sprite patterns in a compact text format
• Testing: Verify expected sprite structure in automated tests
• Analysis: Quickly identify sprites with similar color distributions
• Debugging: Understand why sprites look different than expected
• Asset Cataloging: Generate searchable metadata for sprite assets

Notes

• This analysis works best with sprites that have distinct color regions
• For sprites with gradients or many colors, consider increasing color tolerance
• The Y-axis is flipped from Unity's texture coordinates to produce top-to-bottom output
• Transparent pixels can be treated as a distinct "color" or ignored based on use case