Protection against denial-of-service from malicious or highly-compressed images

[coobird]

Highly-compressed images in the form of large PNGs or malicious PNG decompression bombs could lead to OutOfMemoryErrors.

While I haven't researched whether decompression bombs can actually happen with the default PNG reader bundled with Java, if such things can happen, then a countermeasure against them would be nice to incorporate in Thumbnailator.

References:

• Defending Libpng Applications Against Decompression Bombs
• The Java Image Processing Survival Guide - Memory Usage
• How to check png file if it's a decompression bomb

[coobird]

Duplicate of #105.