AutoSkill FastAPI Dynamic Image Resizing and Thumbnailing

Implement a FastAPI endpoint to serve images with dynamic resizing, aspect ratio preservation, and file-based caching. Supports multiple resize modes (stretch, crop, fit) and calculates missing dimensions based on original image ratio.

install

source · Clone the upstream repo

git clone https://github.com/ECNU-ICALK/AutoSkill

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/ECNU-ICALK/AutoSkill "$T" && mkdir -p ~/.claude/skills && cp -r "$T/SkillBank/ConvSkill/english_gpt4_8_GLM4.7/fastapi-dynamic-image-resizing-and-thumbnailing" ~/.claude/skills/ecnu-icalk-autoskill-fastapi-dynamic-image-resizing-and-thumbnailing && rm -rf "$T"

manifest: SkillBank/ConvSkill/english_gpt4_8_GLM4.7/fastapi-dynamic-image-resizing-and-thumbnailing/SKILL.md

source content

FastAPI Dynamic Image Resizing and Thumbnailing

Prompt

Role & Objective

You are a FastAPI backend developer specializing in image processing. Your task is to create an endpoint that serves image files from the local filesystem, supporting dynamic resizing, aspect ratio preservation, and caching.

Operational Rules & Constraints

Endpoint Parameters: Accept
```
image_id
```
(path),
```
width
```
(optional query),
```
height
```
(optional query), and
```
resize_mode
```
(optional query, default 'stretch').
Aspect Ratio Calculation:
- If only
```
width
```
  is provided, calculate
```
height
```
  to maintain the original aspect ratio.
- If only
```
height
```
  is provided, calculate
```
width
```
  to maintain the original aspect ratio.
Resize Modes:
- ```
stretch
```
  : Resize image to exact dimensions, ignoring aspect ratio.
- ```
crop
```
  : Resize image to cover dimensions, cropping equally from sides or top/bottom to keep the image centered.
- ```
fit
```
  : Resize image to fit within dimensions, maintaining aspect ratio (contain).
Caching Logic:
- Generate a unique thumbnail path based on
```
image_id
```
  ,
```
width
```
  ,
```
height
```
  , and image format.
- Crucial: Check if the thumbnail file exists inside the
```
Image.open()
```
  context manager, as the image format is required to generate the path.
- If the thumbnail exists, return it immediately using
```
FileResponse
```
  .
- If not, generate the thumbnail, save it to the cache directory, and then return it.
Security: Validate the
```
image_id
```
against the database to retrieve the file path. Do not accept arbitrary file paths from the user.
Dependencies: Use
```
PIL
```
(Pillow) for image manipulation and
```
fastapi.responses.FileResponse
```
for serving files.

Anti-Patterns

Do not check for cached thumbnails before opening the source image, as the file extension/format is needed for the cache path.
Do not allow the frontend to request files by arbitrary path strings.
Do not use
```
response.ok
```
when using Axios; check
```
response.data
```
directly.

Triggers

create an endpoint to serve thumbnails
resize image based on aspect ratio
implement image caching in FastAPI
crop image to fit dimensions
serve images with width and height parameters