In last article, I used wkhtmltoimage to create an about 73M png file,  and in this article, I want to optimizer it with OptiPNG,
apt-cache search optipng
output
optipng - advanced PNG (Portable Network Graphics) optimizer pngnq - tool for optimizing PNG (Portable Network Graphics) images pngquant - PNG (Portable Network Graphics) image optimising utility trimage - GUI and command-line interface to optimize image files
Let’s try optipng
apt-get install optipng optipng -o 7 phpinfo_optipng.png
From the following screenshot, we notice after optimized with optipng, 73M png becomes only 1.3M
- Â phpinfo.pdf
- phpinfo_optipng.png, optimized with optipng
- phpinfo.png(created with wkhtmltoimage)
Other 3 software I have not tested.
OptiPNG is a PNG optimiser 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.
Pngnq is a tool for quantizing PNG images in RGBA format.
Pngnq is an adaptation by Stuart Coyle of Greg Roelf’s pnqquant using Anthony Dekker’s neuquantalgorithm.
pngquant is a command-line utility to quantize and dither 32-bit RGBA PNGs down to 8-bit (or smaller) RGBA-palette PNGs, usually with a significant reduction in file size.
Trimage is a cross-platform GUI and command-line interface to optimize image files for websites, usingoptipng, pngcrush, advpngand jpegoptim, depending on the filetype (currently, PNG and JPG files are supported).