batch mode not working for color reduction

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batch mode not working for color reduction

(16 posts) (8 voices)

Started 8 years ago by tby
Latest reply from gavinharriss

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tby
Member

Hi,

I am using RIOT and a few other similar programs. Riot is by far better in png file compression and image quality after.

But, when I batch process a lot of png-24 images and reduce color to 256, the first few files look good but as I check more files, the image quality is bad on some. This is not the case when I do files individually.

What I see here is that the batch processing is not keeping the colors at 256. It seems to change early in the batch processing, and lower color numbers like 32 or 13 are used on the conversion of the later files in the batch, making image quality very bad.

Not sure if there is a solution. Probably is a programming bug. This is a problem only when batch processing 10 or more png-24 to png-8 images. But doing it one image at a time works perfectly, Just that I have a few thousand png images to convert for my website, and the batch is not working right.

Other programs batch without problems, but with larger file sizes and lower quality images on many. That is why I would like to keep using RIOT.

Any fix to this problem?

thanks

Posted 8 years ago #
luciansabo
Key Master

Thank you for posting this. I will investigate it.

Posted 8 years ago #
snowfall
Member

I have exactly the same problem with color reduction.

I process about 1300 PNGs, all of them have ~256 color. (some have just 2)

When the batch mode reach to the 2-color-image, it set "Reduce color" to 2 for all next image, make all image after this one look very bad. I'm sure this is a programming bug :(

(my E. is bad, I don't know how to tell you what I'm thinking =="")

Posted 8 years ago #
gavinharriss
Member

I'm also experiencing this issue in batch mode.

I process about 700,000 map tiles for http://www.topomap.co.nz so this issue becomes quite apparent.

Here's a few example tiles from the same batch in case it's useful:

How it should look:
static.topomap.co.nz/tiles-topo50/15-31721-11878.png
What it comes out as:
postimg.org/image/pe0k982hb/ec81ce3a/

How it should look:
static.topomap.co.nz/tiles-topo50/15-31721-11881.png
What it comes out as:
postimg.org/image/6ewr7kk4l/879b0a90/

Posted 8 years ago #
luciansabo
Key Master

What mode are you using ? full auto ?

Posted 8 years ago #
ozzymuppet
Member

I can confirm this is true, it's broken in Version 0.6.

When using PNG and selecting a custom number of colors, it works fine in manual mode, but using batch it ignores the custom numer of colors you've selected and applies whatever you've selected in the dropdown (eg. 16) or some other very low number, making the images look horrible and unuseable.

Good news is that it's not broken in the old version (google riot-0-4-6-es-en.zip) so I'm relying on that now.

Pity the developer seems to have abandoned this? Oh well, some things are more important than supporting free software for free :) hehe. Great programme though, surprisingly the only free option around that does proper batch compression.

Posted 6 years ago #
luciansabo
Key Master

Not abandoned, just a long hiatus. I will look into this. If I can find the issue quickly it's gonna be fixed in 0.6.1 coming soon

Posted 4 years ago #
luciansabo
Key Master

I couldn't replicate, but I will keep an eye on this.

Posted 4 years ago #
snowfall
Member

I will try to replicate this, as it is (and maybe was) a bug of an (much) older version.
Anyway, great to hear from you after a long time.

Posted 4 years ago #
paulnaude01
Member

Thanks for a brilliant tool! but this problem still exist in 0.6.1. I make to sure to set the PNG compression settings I want, then go to batch mode, add the images, set the output directory and go. The end result is black and white images and the colour setting reduced to 2.

Posted 4 years ago #
andrewk89
Member

I had a similar issue with batch processing of JPEG. The answer I got was more or less:

"manual mode and batch mode don't communicate with each other. Batch mode has its own settings which are not exposed to the user. The automatic settings it chooses is not documented".

I'm heavily paraphrasing, but that is what I gathered. Original discussion here: //luci.criosweb.ro/riot/bbpress/topic.php?id=505

There are a couple of requests I'd like to make regarding this topic and the related topic:

1. It would really help users if batch mode settings were documented. What is the software doing when it loads an image? What settings is it choosing? What decisions is it making? Transparent documentation helps users better understand what the results will be. It also helps alleviate misunderstandings and to find root cause of bugs.

2. It would be a great enhancement if there was a way to import the manual mode settings into batch mode, or otherwise flag batch mode to use the settings from the manual mode tab. Because of Point #1, I think several users, including myself, believe this is a bug / broken feature, but luciansabo's responses say this was not part of the software specification.

Posted 4 years ago #
ako
Member

Hi, +1 for this issue in Riot 1.0.1. Now I don't understand how to reduce, say, 30 images in the batch mode (plus manual) to exact color palette (128 for example) which I've chosen. It downgrades to single-digit colors at the end of the queue.

And of course the auto mode doesn't allow to choose an exact color palette and algorithm as well.

I think that manual mode should lock color reduction settings for both single and batch optimizations.

Posted 2 years ago #
luciansabo
Key Master

It should lock them but this looks like a bug, which I need to replicate first

Posted 2 years ago #
ako
Member

Steps to reproduce:

1. Save these PNGs as file:
https://www.pngmart.com/files/7/Gallery-PNG-File.png (rename to 1-* to set place in the queue)
https://www.pngmart.com/files/7/Gallery-PNG-Transparent-Image.png (rename to 2-*)
save as PNG screenshot of the page: https://www.pngmart.com/image/tag/gallery (rename to 3-*)

2. Set these settings: https://i.imgur.com/Jy81Mnu.png (Optimal 256 colors pal., Compression max., NeuQuant) and switch to manual mode.

3. Add files to batch and optimize them: https://i.imgur.com/HBwWMc0.png

4. 3-Screenshot.png will downgrade to 1-bit image: https://i.imgur.com/r5uUFdu.png

And the settings will be like: https://i.imgur.com/cbiOfj3.png

Posted 2 years ago #
luciansabo
Key Master

Thanks. I will look into it when I'll have some free time

Posted 2 years ago #
gavinharriss
Member

Here's the settings I was using that resulted in bad results:

https://imgur.com/a/4U79UA5

Posted 2 years ago #

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