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I have been observing odd behavior on our WebGL implementation of our GUI, particularly disappearing PNG Images. This is happening with several of our images, but our keypad is the most notable example.
I will describe the implementation and behavior below. 

This is the PNG Image that we have broken into frames to use for our keypad. 


Our keypad object consists of 13 image objects showing each of the figures in the image


We are using the PNG Decoder class. The image object is an ExternBitmapSync object. This works fine for out console UI which is on IMXRT, but it behaves strangely in WebGL.


When the Keypad Dialog is called, the images will be missing.


This is how it should look:


This is how it appears on WebGL:

The images will appear when interacted with, but only one-by-one:


Sometimes, the keypad will appear correctly - which adds another unexplained variable. Is there any explanation for this odd behavior, and any way to change the settings on the object to ensure that the Keypad will always appear when the dialog is loaded?

Thank you, 


1 Answer

0 votes
Hello Liam,
which version of Embedded Wizard and which version of the custom module 'PNG Decoder' do you use?

Did you set the property 'RequestedNoOfFrames' for your external ressource?

With kind regards,
Hi Rudolf,

I appreciate the response. I am on EW Version 12.03 - but I am unclear the version of PNG Decoder Unit. How could I check that?

My guess is that it was the version associated with EW 9.30 as we updated not too long ago and I don't recall updating the PNG Decoder.


And yes, the RequestedNoOfFrames is set to 13 and this still occurs - however I believe the frame slicing is correct since the images will appear correctly after they are interacted with.

Thank you,
Hi Loam,
Within the unit PngDecoder, you will find the 'Version' sting constant.
Please note that the PNG decoder module are currently offered for Embedded Wizard versions 9.30, 10, 11. (See: https://www.embedded-wizard.de/pricing/gui-services#png-decoder)
Updating to Embedded Wizard 12 was not available so far.

If you need more information here, you can contact me directly.

With kind regards,
Hi Again Rudolf,

I am using version 1.02.00 of the PNG Decoder. I wasn't aware that it was not offered for EW 12.03 but everything seems to be integrated fine as of now, aside from this issue. Is there any advice on what I could change in order to address this problem?

Thank you,

Meanwhile Version 1.06 is available and Version 1.07 is in progress. I just tested the WebGL frames using Embedded Wizard 12 and it seams to be fine.
So please contact me via rudolf.leberfinger@tara-systems.de to check the upgrade.

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