Seg fault crash with ImageOptimizer.LosslessCompress for a specific jpg

[dabutvin]

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

I have a jpg that, when running ImageOptimizer.LosslessCompress() causes a seg fault

Segmentation fault: 11

This happens every time and has reproduced on windows and mac with the latest Magick.NET 7.10.2
Note: this does not crash when calling Compress(). It only crashes when calling LosslessCompress().

I can repro this issue with OptimalCompression on and off, and with IgnoreUnsupportedFormats on and off.

Steps to Reproduce

I have a simple repro set up here: https://github.com/dabutvin/SaskArtists/tree/debug
This is a fork from the original issue trimmed down to a single image and includes a console app that demonstrates the failure. I could not get any additional logs out even when enabling the debug events.

Here is the console app that points to the troublesome image with a relative path
https://github.com/dabutvin/SaskArtists/blob/debug/magick/Program.cs

This is the image file: https://github.com/dabutvin/SaskArtists/blob/debug/www/artists/rarnott/images/snowy_painting.jpg

System Configuration

• Magick.NET version: 7.10.2
• Environment (Operating system, version and so on): MacOS Mojave 10.14.2 + Windows running in Azure Functions Consumption environment

[dlemstra]

Thanks for finding this. This image contains a huge marker that is split up. The current code cannot handle that. And there is an incorrect buffer check that causes this access violation. Will take a look at it next week.

[dabutvin]

Awesome! Let me know how it goes or if you need anything.