Maingron
TOVoptiPNG 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 and corrections.
Oliver Grimm ๐ช๐บever heard of #optipng and #jpegoptim on #linux? With these two small #cli tools one can shrink most png and jpeg files without additional quality loss. These tools simply try all possible combinations of compression parameters. If they find a better combination than the current one, they apply it. On average this leads to an additional compression of -10% without compromising the quality any further. Have fun :-)
Maciej Barฤ
lopeztel 
#jpegoptim & #optipng are nice tools that can help you optimize your images.
Output file size = 5897157 bytes (3181925 bytes = 35.05% decrease)
Lemming
skunksarebetter#OptiPNG is a lossless #PNG optimizer.
OptiPNG recompresses PNG files to decrease their size. This process is lossless, meaning the contents of the images are exactly the same once decompressed. OptiPNG can work on several formats, including #TIFF and #GIF, outputting an optimized PNG version of whatever input is given. OptiPNG can also verify the integrity of an image and recover metadata.
Website ๐๏ธ: http://optipng.sourceforge.net/
apt ๐ฆ๏ธ: optipng
โ ๏ธ Grumpy Oldman