OptiPNG – advanced PNG optimizer

OptiPNG is a PNG optimizer that recompresses image files to a smaller size, without losing any information. This program also converts external formats (BMP, GIF, PNM and TIFF) to optimized PNG, and performs PNG integrity checks, corrections, metadata recovery and pixmap-to-PNG conversion.

OptiPNG optimizes PNG files, i.e. reduce their size to a minimum, without losing semantic information. In addition, this program shall perform a suite of auxiliary functions like integrity checks,

The optimization attempts are not guaranteed to succeed. Valid PNG files that cannot be optimized by this program are normally left intact; their size will not grow. The user may request to override this default behavior.

Features include:

• Lossless compression tool for PNG images. It can also convert non-PNG files (BMP, GIF, PNM and TIFF) into compressed PNG file.
• Encoding and optimization options:
  • Select the optimization level:
    • The optimization level 0 enables a set of optimization operations that require minimal effort. There will be no changes to image attributes like bit depth or color type, and no recompression of existing IDAT datastreams.
    • The optimization level 1 enables a single IDAT compression trial. The trial chosen is what OptiPNG thinks it’s probably the most effective.
    • The optimization levels 2 and higher enable multiple IDAT compression trials; the higher the level, the more trials.
  • Filters – select the PNG delta filters. The filter values 0, 1, 2, 3 and 4 indicate static filtering, and correspond to the standard PNG filter codes (None, Left, Up, Average and Paeth, respectively). The filter value 5 indicates adaptive filtering, whose effect is defined by the libpng library used by OptiPNG.
  • Other options are available.
•  Error recovery.
• Simulation mode – performs the trials but doesn’t create output files.

Website: optipng.sourceforge.net
Support:
Developer: Cosmin Truta and contributors
License: zlib license

OptiPNG is written in C. Learn C with our recommended free books and free tutorials.

Return to Command-Line Image Compression Tools

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