Difficulty saving GIFs

[bannerman100]

I used Windows Paint up to Vista, primarily for simple electrical and engineering diagrams saved as GIFs.  It was a perfect program for my purposes !

But Paint in Windows 10 sabotages and changes the colours in my GIF images (and is a nightmare of complication), so I downloaded Netpaint.

I opened one of my GIFs in Netpaint, and tried to save the file.

But then I was confronted by a dialog box demanding "Quantization algorithm", "Dithering level" and "Transparency threshold".

I have never heard of these things, and I don't need them !   I want to save simple GIF images as I did in XP or Vista Paint, which had no such demands.

Is there a way to save my GIFs without all this complication ?   Or is there a "How to save GIFs" page that explains it all ?

[midora]

Hi @bannerman100you have to know that the gif file format is quite old and just allows a maximum of 256 different colors.

But paint.net allows you to use millions of different colors. Just drawing a line may create hundreds of new colors in your image.

Now if you like to save the edited image as gif you need a process to reduce the amount of colors back to the maximum of 256.

This process is called quantization. You need it or you can not save the image as gif.

If you do not depend on the original 256 colors

 

 

 

 

[Red ochre]

Hello Bannerman100, welcome to the forum!

 

1. Quantization algorithm: A paint.NET (Pdn) image is 32 bit, 24 of those bits are used for colour, this means 2 to the power of 24 colours = 256 * 256 * 256 = 16777216 possible colours! (and 256 levels of opacity{0 to 255}).
Now the Gif file type can only save in 8 bit (or 2 to the power of 8 = 256 possible colours {255 if transparency is used, I assume}), so there needs to be some way of deciding which gif colour is used to represent a Pdn colour.
The choice is is 'Octree' or 'Median' cut = Octree seems to give better results and is set as the default.

 

2. Dithering level: Now if a Pdn colour is nearly halfway between the two possible Gif colours what do you want to do?
As an extreme example imagine you want to save a mid-grey colour in a black OR white format! - all black or all white?... or you could randomly apportion pixel colour to be black or white, which from distance would look grey. Think how shading is done on an old engraving.
Compressing a 24bit image to an 8bit image uses the same idea to make colours appear more accurate.
For a circuit diagram I would think zero dithering would suit you - unless it gives false colours for resistor values or other colour coding?

 

3. Transparency threshold: Pdn has 256 levels of opacity/transparency but Gif only has two - fully opaque or fully transparent. So at what point do you want semi transparent pixels to be represented as opaques ones?
I suggest using the default value of 128 and look at the preview image - are any important bits lost? - serifs of letters or other details. If so reduce the threshold.

I'm no expert on file types, so hope I haven't misled you... I'm sure to be corrected if I have!
The concepts are actually simple but the terminology can get in the way sometimes... Just click 'Default' and save!😁

 

@Midora just explained all that in a greatly compressed format! 😉

[midora]

If you do not depend on the original 256 colors then just use the default settings and press ok.

 

Just to finish the sentence 😉

No idea why I have to fight with this forum in the last months. But tries to edit my post always return with

 

"This comment can no longer be edited. It may have been moved or deleted, or too much time may have passed since it was posted for it to be edited."