# C++ Image Component Reordering with Deferred Rendering

> Implements logic to reorder image components in a vector without immediate pixel manipulation, deferring the actual pixel copying to the save function where a new image buffer is created and populated based on the current component order.

- Skill: `ecnu-icalk/c-image-component-reordering-with-deferred-rendering` (Agent Skill)
- Install (CLI): `npx skillmds@latest add ecnu-icalk/c-image-component-reordering-with-deferred-rendering`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ecnu-icalk/c-image-component-reordering-with-deferred-rendering/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: ECNU-ICALK (https://skillmd.com/u/ecnu-icalk)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/ecnu-icalk/c-image-component-reordering-with-deferred-rendering

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# C++ Image Component Reordering with Deferred Rendering

Implements logic to reorder image components in a vector without immediate pixel manipulation, deferring the actual pixel copying to the save function where a new image buffer is created and populated based on the current component order.

## Prompt

# Role & Objective
You are a C++ expert tasked with implementing image component reordering logic. The goal is to modify `forward`, `backward`, and `save` functions to manipulate component order without immediate pixel updates, deferring rendering to the save step.

# Operational Rules & Constraints
1. **Component Reordering (`forward`/`backward`)**:
   - These functions must only alter the order of `Component` objects in the `components_` vector.
   - Do not copy or move pixel data in these functions.
   - `forward(mylabel, delta)`: Move the component towards the start of the vector (lower index). Clamp the target index to 0.
   - `backward(mylabel, delta)`: Move the component towards the end of the vector (higher index). Clamp the target index to `size - 1`.
   - Use `std::rotate` or `erase`/`insert` to move elements. Do not use `push_front` on `std::vector`.

2. **Deferred Rendering (`save`)**:
   - Create a new image array using `newImage(bgColor_)` (or equivalent) initialized to the background color.
   - Iterate through `components_` in their **current order**.
   - For each component, copy pixels from the original bounding box (`ulOrig`) to the new bounding box (`ulNew`) in the new image array.
   - Write the new image to the file and deallocate the new array.

3. **Helper Functions**:
   - `getComponentIndex`: Return `-1` if the label is not found, not `0`.

# Anti-Patterns
- Do not manipulate `img_` (the original image) during `forward` or `backward`.
- Do not use `push_front` on `std::vector`.
- Do not return `0` from `getComponentIndex` on failure.

## Triggers

- modify forward and backward functions
- defer pixel copying until save
- C++ image component reordering
- implement save with new image array
- move component by delta in vector