How can I make images converted by NConvert smaller?

Question

I am using nconvert to convert screenshots generated by "The Elder Scrolls Online", which are in BMP, to PNG. 1 BMP has around 7 MB, the resulting PNG has about 3MB. This is still very big to upload and drains my cloud storage as well as traffic.

Is there any way to make them a bit smaller while not losing much quality? This is the batch script I use:

nconvert -o converted\%%.png -out png *.bmp 

I could not find any option when I launched -help that would do this.

Answer 1

First of all, PNGs maybe output with alpha channel (i.e. 32 bit), so if you don't need alpha channel in your images, be sure that you specify that in nconvert options.

Also depending on your images, it may be possible to save them as 8-bit PNGs. This may significantly reduce the file size, but at the cost of color reduction.

If your images are photos, and absolutely finest quality is not required, then you may consider JPG format instead as it provides much better compression and smaller sizes with very similar-looking results.

You can also try additional tools like OptiPNG