> ## Documentation Index
> Fetch the complete documentation index at: https://docs.bedrock.cv/llms.txt
> Use this file to discover all available pages before exploring further.

# Overlays

> Access drawing comparison results.

Overlays are the result of comparing two [Blocks](/cms-api/resources/blocks) from different drawing revisions. They contain aligned images showing additions (green) and deletions (red).

## Endpoints

| Method   | Endpoint                                                       | Description          |
| -------- | -------------------------------------------------------------- | -------------------- |
| `POST`   | [`/drawings/{id}/compare`](/cms-api/overlays/compare-drawings) | Compare two drawings |
| `POST`   | [`/sheets/{id}/compare`](/cms-api/overlays/compare-sheets)     | Compare two sheets   |
| `GET`    | [`/overlays`](/cms-api/overlays/list)                          | List overlays        |
| `GET`    | [`/overlays/{id}`](/cms-api/overlays/get)                      | Get overlay details  |
| `DELETE` | [`/overlays/{id}`](/cms-api/overlays/delete)                   | Delete an overlay    |

## Overlay Object

| Field           | Type     | Description                                                |
| --------------- | -------- | ---------------------------------------------------------- |
| `id`            | string   | Unique identifier (e.g., `ovl_01JABCD123`)                 |
| `block_a_id`    | string   | Source [Block](/cms-api/resources/blocks) (older revision) |
| `block_b_id`    | string   | Target [Block](/cms-api/resources/blocks) (newer revision) |
| `job_id`        | string   | Comparison job that created this overlay                   |
| `uri`           | string   | Combined overlay image URL                                 |
| `addition_uri`  | string   | Additions-only image URL                                   |
| `deletion_uri`  | string   | Deletions-only image URL                                   |
| `aligned_a_uri` | string   | Aligned source block image                                 |
| `aligned_b_uri` | string   | Aligned target block image                                 |
| `score`         | number   | Similarity score (0-1, lower = more changes)               |
| `summary`       | object   | Change statistics                                          |
| `changes`       | array    | Detected changes (after change detection)                  |
| `created_at`    | datetime | Creation timestamp                                         |

## Similarity Scores

| Score     | Interpretation                       |
| --------- | ------------------------------------ |
| 0.95+     | Nearly identical, minor changes      |
| 0.80-0.95 | Moderate changes                     |
| 0.60-0.80 | Significant changes                  |
| \< 0.60   | Major revisions or different content |