Paint compress PNGs better than RIOT?

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Paint compress PNGs better than RIOT?

(10 posts) (3 voices)

Started 6 years ago by axdoomer
Latest reply from wilk

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axdoomer
Member

I'm drawing UML diagrams on paint. The two main colors are white and black. White is mostly in the background and the black is used to draw the boxes. There is text in the boxes. The font is a in TTF format, so it has pixel sub-sampling. When I save my diagram with pain, it's a few KBs big. When I try to optimize it with RIOT, the PNG gets three times bigger! The PNG is in 24-bit format. RIOT only seems to be able to produce a smaller file using the GIF format.

Why does Paint produces smaller PNG than RIOT?

Posted 6 years ago #
luciansabo
Key Master

did you used color reduction in RIOT ? If you have RIOT 0.5, have you chosen at least medium compression or a better compression strategy ?
That PNG should be optimized with RIOT as 8 bit grayscale with max 64 colors from what you are describing.

Posted 6 years ago #
axdoomer
Member

Even in 16-color, RIOT can't match Paint.

Posted 6 years ago #
luciansabo
Key Master

can you post the image somewhere ?

Posted 6 years ago #
axdoomer
Member

On (remove the spaces) www. mediafire . com /download/xw4i6v1z445pz2t/png_images.zip

The PNGs name pretty much explain what happens. You can play with them and guess what in the algorithm causes this. I'd like to know. I thought PNG was better than GIF on every images. Also, Paint made a smaller PNG than RIOT. I don't really know what makes the image so special that the size becomes smaller in Paint. There a lot of white in these pictures.

In the first file, a 256-color PNG is bigger than a 256-color GIF.

In the second file, a PNG generated by RIOT is 23KB while to one made with Paint is 13KB.

Give me news about that. Thanks!

Posted 6 years ago #
wilk
Member

Clearly you are not using RIOT with optimum settings or simply misusing it. No wonder true color image is much larger than indexed one.

png_image_is_bigger_than_gif_in_256_color.png (59662)
gif, optimal 256, fast = 22525
png, optimal 256, maximum, fast = 18793

riot_png_is_much_bigger_than_paint_png.png (13971)
png, saved by Paint = 26087
png, optimal 256 (reduced to 13), maximum, fast = 3899
above png + built-in pngout = 3853
png, optimal 256 (reduced to 13), maximum, slow (nq) = 3850
above png + built-in pngout = 3796

Posted 6 years ago #
axdoomer
Member

I'm not doing anything wrong! My true color PNG from RIOT is 23KB and my true color PNG from Paint is 13KB.

Posted 6 years ago #
wilk
Member

png, truecolor, maximum = 9300 (9 kB)
above png + pngout = 3723 (3,6 kB)

RIOT: 0.5.2
PNGout: Feb 13 2015

Are you sure you are doing everything ok? Because even using "low" compression I can get the worst case with 10831 bytes large.

BTW. Keep notice that pngout dropped planes to 4 bpp. There is no need to save image with 13 colors as a true color.

Info for luciansabo:
When I use the built-in PNGout optimizer (which is actually plugins\pngout.exe - I also updated it) I get 3744 bytes image. When I add custom optimizer with params "/y /force {IMAGE_FILE}" I get 3723 bytes. What settings do you use? I used TweakPNG to notice that your settings do not drop pHYs chunk.

Posted 6 years ago #
axdoomer
Member

(image link, remove spaces) i. imgur . com / T8i7YmL.png

I was comparing RIOT's 24-bit PNGs VS Paint's 24-bit PNGs.
In the picture, the picture on the left is from Paint and on the right it's the result from RIOT.

I have downloaded the latest version and it seems that RIOT does make smaller images now. May be there was some problem in older versions and it has been fixed, although the new version is very slow.

Posted 6 years ago #
wilk
Member

No wonder it was larger - you've used interlaced PNG.

About speed issue: If you don't need to squeeze image merciless than try medium (default) compression.

Posted 6 years ago #

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