Question 1

How fast is fpng compared to stb_image?

Accepted Answer

fpng encodes PNGs 12-19x faster and decodes its own files 2.5-3x faster than stb_image, with similar or smaller file sizes, as demonstrated in the README benchmarks using 303 test images.

Question 2

Can fpng read any PNG file from the internet?

Accepted Answer

No, fpng's fast decoder only works on PNGs it created. For other PNGs, it returns FPNG_DECODE_NOT_FPNG, so you need a fallback like libpng or Wuffs, adding extra handling.

Question 3

How to integrate fpng into a C++ game engine?

Accepted Answer

Copy fpng.cpp and fpng.h into your project, include the headers, and call fpng::fpng_init() once at startup. Use the provided encode/decode functions with 3 or 4 channels for images.

Question 4

What's better for compression, fpng or lodepng?

Accepted Answer

Lodepng generally achieves smaller file sizes but is much slower (e.g., 6x slower encoding in benchmarks). fpng sacrifices some compression for speed, making it better for performance-critical tasks.

Question 5

Does fpng support alpha channels?

Accepted Answer

Yes, fpng handles 32bpp images with alpha, but it doesn't automatically detect unused alpha—you must specify 3 or 4 channels during encoding, and decoding can discard or add alpha as needed.

Question 6

How to build fpng on Linux for maximum speed?

Accepted Answer

Use cmake with -DSSE=1 and compile with -msse4.1 -mpclmul flags to enable SSE optimizations. Remove -DSSE=1 on non-x86 systems, but performance will be lower.

Question 7

Is fpng good for embedded systems with low memory?

Accepted Answer

Yes, fpng has a low memory footprint with minimal temporary allocations, and it can decode directly into output buffers, making it suitable for resource-constrained embedded applications.

fpng

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