I'm using a Vagrant VM to mirror the client's environment as closely as I can. As part of our build process we do no optimization of assets early on; that comes as we're ready to take a site live. Needless to say, this issue is beginning to worry me as we need to take the site live very soon.

I use ImageOptim to automate optimization of image assets, which runs a whole series of tools (Zopfli, PNGOUT, OptiPNG, AdvPNG, PNGCrush). I always set the optimizations to their maximum setting.

After optimization, my PNGs start looking like this:

What's weird is, if I serve the same file through my Mac's copy of Apache, not through Vagrant, the image loads fine. In fact, the only time it's ever corrupt like this is when the image is served from the Vagrant VM and its install of Drupal. All optimized JPEGs display only the first ~20% of the image. And PNGs, depending on the image, may show either a portion or the "progressive"-style corruption below. The browser itself makes no difference, the same browser will serve an uncorrupted image from my Mac's Apache instance and a corrupt image from the VM.

When I disable all PNG optimizations except PNGCrush, and the removal of the PNG metadata, the image is served corrupted.

I'm optimizing JPEG images with JPEGmini.

The server is running CentOS 5.9, Apache 2.2.3-85, PHP 5.3.3, and Drupal 7. As best as I can tell the error lies somewhere within the VM, either with Apache or with (perhaps) the network stack. Seems like the tools that optimize the compression of the PNGs and JPEGs are what trigger this error. I've already determined that the .htaccess file isn't interfering with how the images load.

What should I try to troubleshoot this?