Module thumbnail 

Thumbnail and preview image generation.

This module provides configuration structures and utilities for generating thumbnail images or sprite sheets from video content. Actual pixel decoding is handled by the caller; this module focuses on timestamp selection, sizing, and nearest-neighbour scaling.

Structs

AnimatedFrame

A single frame in an animated thumbnail.

AnimatedThumbnail

An animated thumbnail consisting of multiple frames with timing.

SpriteSheet

A sprite sheet: a single wide RGBA image that tiles multiple thumbnails left-to-right, top-to-bottom.

SpriteSheetConfig

Configuration for generating a sprite sheet from a video.

Thumbnail

A single generated thumbnail.

ThumbnailConfig

Configuration for thumbnail generation.

ThumbnailExtConfig

Extended thumbnail configuration with quality profile support.

Enums

ThumbnailFormat

Output format for generated thumbnails.

ThumbnailQualityProfile

Quality profile for thumbnail generation.

ThumbnailStrategy

Strategy for selecting thumbnail timestamps.

Functions

compute_thumbnail_timestamps

Computes a list of timestamps (in milliseconds) at which to capture thumbnails.

compute_uniform_timestamps

Computes count uniformly spaced timestamps across duration_ms.

format_vtt_time

Formats a millisecond timestamp as a WebVTT time string (HH:MM:SS.mmm).

generate_vtt_track

Generates a WebVTT thumbnail track file from a sprite sheet and its URL.

scale_thumbnail

Scales a source image buffer to the destination dimensions using nearest-neighbour sampling.

select_smart_thumbnails

Selects the count most visually interesting thumbnails from a set, ranked by spatial luminance variance.

thumbnail_variance

Computes the spatial variance of an RGBA thumbnail’s luminance.