Reduce a PNG Image

Use the PNGReduceFile and PNGReduceData methods to losslessly reduce PNGs in memory or on disk without first decompressing to a DIB, thereby saving processor time and system resources.

Supports 1, 4, 8, 16, and 24-bpp PNGs.

File size reduction is accomplished by removing select pieces of metadata and other possible color and/or transparency reductions of the source PNG.

Compression ratios will vary depending on the source PNG. For example, applying either PNGReduceFile or PNGReduceData to a 1280x960, 24-bit color PNG reduces its size from 1754 KB to 1377 KB. However, applying either PNGReduceFile or PNGReduceData to the output PNG results in no further size improvements.

Reduce a PNG on Disk

To reduce PNGs on disk, just specify the path to the source PNG and the path to save the re-compressed PNG using the PNGReduceFile method.

Reduce a PNG in Memory

To reduce PNGs expressed in memory, first read the source PNG data into the variant and then re-compress the PNG data using the PNGReduceData method.