Apparent memory leak with image resize

Prerequisites

• I have written a descriptive issue title
• I have verified that I am using the latest version of Magick.NET
• I have searched open and closed issues to ensure it has not already been reported

Description

My issue seems similar to this comment in #340, but it doesn’t seem to have ever been addressed. It appears that MagickImage.Resize has a memory leak. I have come to this conclusion experimentally rather than via debugging the library manually, but the snipped code below does not leak memory if I comment out the image.Resize(...) line, whereas it does leak memory otherwise. I have observed this in Docker (based on the image mcr.microsoft.com/dotnet/core/sdk:2.2).

Steps to Reproduce

The container’s memory balloons if I continuously make requests to the endpoint containing this code. I imagine simply calling this code in a while loop would exhibit the same behavior (I can provide the full controller if necessary, but figured I would limit it for brevity).

// ImageController.cs
var format = ...; // computed from URL

// imageData is a byte array
Debug.Log($"Creating image object...");
using (var image = new MagickImage(imageData, format))
{
    if (image.Width <= 512 && image.Height <= 512)
    {
        var str = new MemoryStream(imageData);
        Debug.Log($"Smaller than 512, returning...");
        return File(str, http.ResponseHeaders["Content-Type"]);
    }

    int targetWidth = Math.Min(image.Width, 512);
    int targetHeight = Math.Min(image.Height, 512);

    var size = new MagickGeometry(targetWidth, targetHeight);
    Debug.Log($"Resizing...");

    // Commenting out this line prevents the code from leaking memory
    image.Resize(size);

    // Save the result
    var data = image.ToByteArray();
    Debug.Log($"Resized, returning...");
    {
        var str = new MemoryStream(data);
        return File(str, http.ResponseHeaders["Content-Type"]);
    }
}

System Configuration

• Magick.NET version: Magick.NET-Q8-AnyCPU 7.21.1.0
• Environment (Operating system, version and so on): Docker Desktop for Windows 10, Docker on Amazon Linux 15. Container based on mcr.microsoft.com/dotnet/core/sdk:2.2
• Additional information:

[kaktuspalme]

Maybe someone will stumble across the same problem as me. I’m using Magick.NET in a ASP.NET Core application inside a linux docker container. An image conversion is triggered by a rabbitmq message. What happened was that the application was using much more memory than it should. After analysing memory and searching for leaks etc. I finally stumbled across this: https://github.com/dotnet/runtime/issues/13301#issuecomment-535641506

Setting the environment to either MALLOC_TRIM_THRESHOLD_=100000 or GLIBC_TUNABLES=glibc.malloc.trim_threshold=100000 as mentioned in the comment above resolved my issue.

[dlemstra]

Ping @shadowndacorner ?