'White Artifatcs' in page viewing of Animated GIF files

[budz45]

Hi,

On my Windows XP sp3 machine I still run XnView win 1.96.1.

This issue is like a bug but I was uncertain where to post this issue.

Basically, I have always noticed with XnView when viewing individual pages to basic 2 frame animate GIF's, I go to the next frame from the 1st default and on the second I often tend to see an 'artifacts' or white lines which distort the other frame. When i open the same animated GIF in PhotoFiltre Studio 9.2 I am able to analyze the frames and notice some things as 'visible'.

I just would like if XnView, upon individual page viewing, retained and displayed the normal and non-artifact frame. I don't want to see these.

Look at my screenshots;

on Xnview win 1.96.1


on Xnview MP 0.31 beta


..in Photofiltre Studio (below) - I can right click on each frame that is represented as a layer and I can toggle the 'visible' on/off to get the proper GIF quality of the frame which I should be seeing in Xnview.


I have uploaded the actual GIF itself, here it is; http://i51.tinypic.com/qmxdzn.gif
(BTW the pretty woman is Liz Bonnin, a British TV presenter)

I have a feeling this is a well known issue of ani GIF's in Xnview. Please anyone or Pierre, shed some light on this issue

[xnview]

The second frame has a transparent index...

[XnTriq]

I have a feeling this is a well known issue of ani GIF's in Xnview. Please anyone or Pierre, shed some light on this issue

When you're flipping through a GIF animation (cmd_PreviousPage / cmd_Page / cmd_NextPage), XnView displays the frames in their optimized (differential) state:

• 
  Frame properties
  [ z00m ]

• 
  Unoptimized animation
  [ z00m ]

“Dirty Rectangle” optimization

Dirty Rectangle optimization refers to a mode of optimization that involves cropping frames in a GIF animation to their smallest needed rectangle. These frames are then placed on top of each other using pixel coordinates for placement.

[...]

Interframe transparency optimization

Another way to optimize an animation is to make redundant portions of animation frames transparent. This often, but not always, results in file size savings. This is done by using two features in the GIF file format: transparency and disposal methods. Some colors in a GIF file can be made transparent, allowing the background image or color to show through them. The same is true for frames in an animation — if parts of the frames are transparent, they show through to any other frames behind them. This is referred to as “Interframe Transparency” (some GIF animation utilities refer to it as “Frame Differencing”).

• Animation support in NCONVERT
• Problem loading animated GIF (ImageWanted>0)
• APNG crashes: incomplete fix

[MaxSt]

How about this one:

[budz45]

How about this one:

No not really any issue with this one. However in the last number of frames with the transparent 'green arrow' I can see some small artifact.

I always notice this 'white artifact' issue for years using Xnview and page-flicking through animated GIF's but not just Xnview alone, some other image viewers too.. Mainly it is animated GIF's with only two frames such as ani GIF's from website banners, ads etc.

Couldn't I just flick through the pages without seeing the artifact or is that impossible?