Fast PNG Compression??

[ElPsyKongroo]

Hi,

i have to compress a large quantity of PNG files for a website, which only takes PNG with less than 6MB. The original files are in the range of 10-30MB so i have to compress them quiet a bit. I have tried PNGGauntlet with PNGOUT and OptiPNG (7) an it took a really long time (CPU 2200G; 3,8GHz; usage 20%).

 

Is there a GPU compression tool using OpenGL or CUDA? Or an other alternativ?

 

[mariushm]

I would launch multiple copies of Irfanview and do batch conversion on different folders in parallel ... as compression to png is single threaded , you'd probably get the best results with 6-8 threads in parallel. 

 

There are applications that do conversions using multiple threads, one was/is even used as a benchmark tool but I don't remember the tool now. 

 

Those tools like pngout and optipng only help you if you have particular images that don't use a lot of unique colors or large areas with same colors. Otherwise, they don't reduce the png image size in a significant enough way. 

 

I would batch convert them once using PNG's compressor at level 9 compression, and then select all the files that are still above your 6 MB threshold and consider more drastic measures, like resizing the image to 75% of original size, or 50% of original size 

 

A 30 MB PNG picture would have to be around 40-60 MB uncompressed ... that's enough for a 8K picture or even bigger... don't tell me you'd actually need that big of a picture. 

If they're scans of papers or stuff like that, maybe consider lowering the color depth to 16 bit (65k unique colors) or even 256 unique colors - it would still retain the color of the paper and the printed text with 256 unique colors.

 

 

[Chris Pratt]

PNG is a lossless format. It employs compression itself to encode all the data as efficiently as possible, but that also means you're not going to get much of a size reduction without an accompanying reduction in colors and/or quality. A 6MB PNG is already physically large, though, so your best bet would most likely be to resize them to a more appropriate size for the application.

[Roswell]

13 hours ago, mariushm said:

A 30 MB PNG picture would have to be around 40-60 MB uncompressed ... that's enough for a 8K picture or even bigger... don't tell me you'd actually need that big of a picture. 

If they're scans of papers or stuff like that, maybe consider lowering the color depth to 16 bit (65k unique colors) or even 256 unique colors - it would still retain the color of the paper and the printed text with 256 unique colors.

 

 

That's not how PNGs work. It's a lossless format and the complexity of the image completely dictates the size. I just finished an 8 bit, 4K sRGB landscape photo that ends up at 34MB after exporting to PNG.

 

A recent logo I made sits at 2.8MB at 10000x10000 when I export it as a PNG... It all depends on the content of the image.