Batch Image Resizer

A Windows desktop app for batch resizing images across folders and subfolders. Built as an improvement on the PowerToys Image Resizer — which only works on individually selected files — this lets you point it at entire folder trees and get on with your day.

Features

• Recursive folder walking — select one or more folders and it'll process everything inside, including subfolders
• Resize presets — common sizes out of the box (Thumbnail up to 4K), or set your own width/height
• Resize modes — Fit, Fill, Stretch, Longest Side, Shortest Side, or scale by percentage
• Output options — overwrite originals, save to a subfolder, a custom folder, or mirror the original folder structure
• Format conversion — keep the original format or convert to JPEG, PNG, WebP, BMP, TIFF, or GIF
• Quality control — adjustable quality for JPEG and WebP output
• Metadata preservation — keeps EXIF, XMP and ICC profiles by default; optionally strip all metadata
• Timestamp preservation — copies the original file's creation and modified dates to the output
• Filename control — add a prefix and/or suffix to output filenames
• Settings are remembered — all your preferences are saved between sessions

Requirements

• .NET 8 SDK
• Windows 10 / 11 (WPF is Windows-only)
• Visual Studio 2022, JetBrains Rider, or VS Code with the C# Dev Kit extension

Building from source

Requires .NET 8 SDK and make.

git clone https://github.com/JezzWTF/resizer.git
cd resizer
make          # debug build
make publish  # self-contained single-file exe → ./publish
make run      # build and run
make clean    # remove build artifacts

To regenerate the app icon after editing icon.svg (requires ImageMagick):

make icon

Test data generation

Use the placeholder generator to create a realistic nested photo library for resize and storage testing.

powershell -ExecutionPolicy Bypass -File .\scripts\generate-placeholder-images.ps1

What it prompts for:

• destination folder
• number of folders
• images per folder
• resolution preset (Mixed 1080p + 4K, 1080p, 4K, or custom)
• output format (jpg or png)
• target JPEG size in MB (approximate, when jpg is selected)

Default test profile:

• Mixed 1080p + 4K preset (70/30 split)
• jpg output
• target JPEG size 3.5 MB

This mode creates master images once, then copies them into the generated folder tree for fast dataset generation.

Stack

• .NET 8 / WPF
• SixLabors.ImageSharp — image processing
• CommunityToolkit.Mvvm — MVVM framework
• Ookii.Dialogs.Wpf — folder picker dialog