Web and WebWorks Development

[polovi]

when i try to return canvas image as image/jpeg with/without image quality is returned only empty data as data:image/jpeg;base64,

simple example here 

http://jsfiddle.net/ptSUd/ or http://www.nihilogic.dk/labs/canvas2image/ convert to JPEG

image/png works fine

[astanley]

Can you clarify what your question is?

Are you seeing unexpected behavior when running your code on the PlayBook, or is this a general question about using canvas?

Thanks!

[polovi]

sorry my mistake, for some reason I did not send the whole query.

I have not a question directly, but rather I wonder if anyone can confirm this behavior in webworks application with tablet OS 2

thanks

[astanley]

Gotcha, I understand now.  I can reproduce your error with your code sample above.

Try changing the data type of the image to the following (jpg instead of jpeg):

dataUrl = canvas.toDataURL('image/jpg');

This seems to work.

I'm curious if Canvas doesn't like the image/jpeg MIME type?  When using that on PlayBook I see a runtime exception in Web Inspector for "GET data:image/jpeg;base64" (where the type is undefined).  When running the same code in Chrome, I see improved results, but it is still erroneous (black background).

[polovi]

When you use "image/jpg" its incorect type and returned image is png as default value same as use image/png as content type

https://bdsc.webapps.blackberry.com/html5/apis/canvas.html#.toDataURL

Description: The argument, if provided, controls the type of the image to be returned (e.g. PNG or JPEG). The default is image/png; that type is also used if the given type isn't supported.

"When using that on PlayBook I see a runtime exception in Web Inspector for "GET data:image/jpeg;base64" (where the type is undefined)."

yes this is the error

canvas.toDataURL can use content types "image/png" and "image/jpeg" with second parametr as qualiti (range 0.1 - 1.0)

http://www.w3.org/TR/html5/the-canvas-element.html#a-serialization-of-the-image-as-a-file

on playbook:

image/png work correct 

image/jpeg return empty data value and result is only data:image/jpeg;base64,

i dont know if image/jpeg before os2 work correctly, but from API reference it seams that it should work but dont work

-----------------

"black background"

its ok original image is transparent which jpeg dont interpretate and use black background color

[astanley]

Alright thanks for helping to flesh this out.

This sounds like a bug in the Web platform on PlayBook.  I'll file an issue in the DIT, and escalate it internally to the browser dev team.

https://www.blackberry.com/jira/browse/TABLET-542

Cheers,