Interface IImageTransformer

Optional server-side image transformer for URL-based transforms (?w=&h=&fit=&format=&q=) produced by CoreUpload.transformUrl() on the client.

CoreUpload ships ZERO image-library dependencies to remain cross-platform and trimming-friendly, so this capability is opt-in. Register an implementation in DI to have the download endpoint honor transform query parameters:

builder.Services.AddSingleton<IImageTransformer, ImageSharpTransformer>();

When no implementation is registered, the download endpoint streams the original bytes and the client / CDN is expected to apply the transform.

Namespace: CoreUpload.Providers

Assembly: CoreUpload.dll

Syntax

public interface IImageTransformer

Methods

TransformAsync(Stream, IQueryCollection, string?)

Transform the supplied image stream per the request query parameters. Recognized keys: w, h (pixels), fit (cover|contain|inside|outside), format (jpeg|webp|avif|png), q (1-100), crop ('x,y,w,h'), blur (radius px), gravity (compass|smart|face), rotate (90|180|270), flip (h|v|hv), grayscale (1), wm (watermark text) and wmpos (compass|center). Use Parse(IQueryCollection) for validated, clamped values instead of re-parsing the raw query. Return (null, null) to fall back to the original.

Declaration

Task<(byte[]? Bytes, string? ContentType)> TransformAsync(Stream source, IQueryCollection query, string? sourceContentType)

Parameters

Type	Name	Description
Stream	source	The original image stream.
IQueryCollection	query	The request query collection.
string	sourceContentType	The original content type, if known.

Returns

Type	Description
Task<(byte[] Bytes, string ContentType)>	The transformed bytes and their content type, or (null, null).