Canvas image blur when multiple time load and save in canvas

[Sanjay Sangwan]

Hello everyone,

I am stuck at the program, where i am loading the image in canvas and save again multiple time. After every time save, its getting blur. Image attached. Pls help me. Thanks in advance.

Sanjay Sangwan

[Chris Ward]

Hello Sanjay

Unfortunately, that is a limitation of App Inventor's Canvas Gadget. 

[SteveJG]

@ Chris  This behavior is not a limitation of App Inventor's Canvas.   The Canvas is part of Android's operating system  https://developer.android.com/reference/android/graphics/Canvas .  The Canvas Object merely provides access to the capability of the Android operating system tools.

@ Sanjay  Make a copy of a copy of a copy using any technique and eventually the final copy loses resolution Sanjay.   Exactly why this happens with your app may have to do with pixel resolution of your device, how you display the image (whether you display it 1:1 or allow the software to shrink the image to fit the Canvas) or something else beyond the capabilities of even the professional compilers.

Regards,

Steve

[TimAI2]

There is a possible, but complicated, workaround, whereby you save the drawing action coordinates rather than the actual drawing, then load these for next time.

Would need to more fully understand your workflow in the canvas to explain further and give examples

See here:

https://groups.google.com/forum/#!category-topic/mitappinventortest/BG9vBHDIXG0

and here

https://groups.google.com/forum/#!category-topic/mitappinventortest/0iU5_b0GOW0

[Chris Ward]

Hi Steve

I believe it really is our limitation, if not in fact a bug, caused by our implementation of the Android Canvas and how the save function works in particular. 

[Italo]

I believe in fact it is a bug of App Inventor, since you can save a picture in the canvas, in FIXED mode and the picture doesn't degrade too much. 

The bigger degradation (I think due to a high compression value) only happens when the screen is set to RESPONSIVE.

Outside App Inventor, that kind of blurring usually happens when saving a JPG with a compression of 85% or more, but in App Inventor, it happens even when saving in PNG format.

[SteveJG]

I do not believe this is a bug in AI.   It is the way App Inventor is designed.   In order for AI to handle graphics simply, the development team came up with compromise code that scales  the screen.

Copy of a copy of a copy of a copy will become blurred.  

[Chris Ward]

Hi Steve

Your explanation really cements the view that the fault is App Inventor's "compromise code". Even a single save results in some degradation and it should be possible to make multiple copies without any degradation. Perhaps Canvas Save File could be set aside as an assignment for an Undergrad to tackle.