Image Management

The Image Management system provides backend functionality for handling image uploads, storage, and serving. It is automatically initialized at application startup and is always available.

Functional areas

Session Management provides the following key functions:

Image storage

• Store images in a blob store
• Manage SourceSets (image pyramids with multiple resolutions)
• Supports png and jpeg formats

Image processing

• Automatically generate thumbnails / scaled versions
• Object-fit support for responsive layouts (FitCover, FitNone)
• Validate file size and dimensions

Use cases

• CreateSrcSet: creates an SrcSet from an uploaded file
• LoadSrcSet: loads a previously stored SrcSet
• LoadBestFit: returns the best image candidate for given dimensions and object-fit
• OpenReader: reads raw image data from the blob store

HTTP endpoint

The HTTP endpoint /api/nago/v1/image exposes stored images over HTTP.

• Accepts query parameters: src (image ID), fit (object-fit), w (width), h (height)
• Returns the best-fit image from a SrcSet
• Sets caching headers for long-term caching (1 year)

This endpoint allows frontend pages to render images dynamically without embedding raw image data.

Code usage

Example: create a SrcSet from an embedded PNG and render it in a page.

package main

import(
	_ "embed"

	"go.wdy.de/nago/application"
	"go.wdy.de/nago/application/image"
	"go.wdy.de/nago/application/image/http"
	"go.wdy.de/nago/application/user"
	"go.wdy.de/nago/pkg/std"
	"go.wdy.de/nago/presentation/core"
	"go.wdy.de/nago/presentation/ui"
)

//go:embed example.png
var embeddedImage []byte

func main() {
	application.Configure(func (cfg *application.Configurator) {
		cfg.SetApplicationID("image.management.example")
		
		file := core.MemFile{
			Filename:     "example.png",
			MimeTypeHint: "image/png",
			Bytes:        embeddedImage,
		}
		
		imgManagement := std.Must(cfg.ImageManagement())
		
		srcSet, err := imgManagement.UseCases.CreateSrcSet(user.SU(), image.Options{}, file)
		if err != nil {
			panic(err)
		}
		
		cfg.RootViewWithDecoration("image_example", func(wnd core.Window) core.View {
			imgURL := httpimage.URI(srcSet.ID, image.FitCover, 800, 600)
			return ui.VStack(
				ui.Text("Example Image"),
				ui.Image().URI(imgURL),
			).Frame(ui.Frame{}.MatchScreen())
		})
	}).
		Run()
}

Dependencies

Requires:

• No other systems

Is required by:

• Signature Management

Activation

This system is activated via:

std.Must(cfg.ImageManagement())

imageManagement := std.Must(cfg.ImageManagement())