Pixels cutting off with roScreen / roBitmap

Archived
1

Hi,

I apologize if this has been answered before. When I try to display an image using the following code, the image always gets cut off on the left side by about 40 pixels. The image is smaller than my screen. I can make it better by using:

Screen.DrawObject(40, 0, bitmap)

instead of:

Screen.DrawObject(0, 0, bitmap)

but I worry that will not work on all TV’s. Does anyone know why the images are getting cut off on the left side and how to fix? Is it my TV, HD in general, etc.? Thanks for your help.

Screen=CreateObject("roScreen")
port = CreateObject("roMessagePort")
Screen.SetMessagePort(port)    
bitmap = CreateObject("roBitmap", "tmp:/image.jpg")
Screen.DrawObject(0, 0, bitmap)
Screen.Finish()
2

Could it be your TV’s overscan? http://en.wikipedia.org/wiki/Overscan

There’s a discussion of safe zones in the Design Guidelines doc: http://sdkdocs.roku.com/display/sdkdoc/ … 2Safezones

3

Thanks. It looks like that is what it is. The list at http://pixelmapping.wikispaces.com/ shows that my Sharp HDTV has a 5% overscan over HDMI.

I am trying to show an image on the screen and have it flush with the left side while showing every pixel but I don’t think that is possible on every TV without giving the user some sort of parameter to set the overscan offset. If anyone has any thoughts I would love to hear them. Thanks.

4

Since every TV has a different amount of overscan, it’s not really possible to do that. The only safe way to display is to respect the safe zones as described in the SDK.

–Mark

5

One of the SDK sample apps has a user-controlled ‘overscan adjustment’ routine that an application could run before displaying the main content - and the results could be saved to the roku registry for all your apps with the same dev key. I forget which sample app had it - but it was like a graphics demo one with color bars and a circle/map type display.