bList Image Resize and Transparency

I

IansResearch

Member

Licensed User

• Feb 2, 2010

• #1

Using latest version of bList 0.92. My application works fine while testing on windows mobile standard screen size. However when I compile(autoscale) app and run on high resolution HTC Touch HD the images appears small in top left corner and the transparency around the edge of the image is not correct infact all the images appear in a white box.

Is bList meant to rescale images and text when compiled autoscaled?
What has happened to the transparency of the images?
If not what do I need to do to correct this problem?

Thank you. :sign0085:

 

derez

Expert

Licensed User

Longtime User

• Feb 2, 2010

• #2

The blist is autoscaled, but the images are loaded according to their size, so what fits a qvga will be only a quarter in vga.

This means that you need to change the size of the image prior to loading it to the list.

You can use img.ZoomImage with the zoom factor defined by screenscaley.

This is what I do in my Family tree to show thumbnails on the list:

B4X:

imfn = AppPath & "\jpg\" & list.Item(i)& ".jpg"
If FileExist(imfn) Then 
   image2.image = imfn
   ImgSize() = img.ImageSize(image2.Image)
   factor = Max(imgsize.hy/320,imgsize.wx/240)
   item.SetImageFromExisting(img.ZoomImage(image2.Image,8*ScreenScaleY/factor))
   item.ImageTop = 1
End If

 

Last edited: Feb 2, 2010

Erel

B4X founder

Staff member

Licensed User

Longtime User

• Feb 3, 2010

• #3

You should set the image size explicitly and it will be auto-scaled correctly:

B4X:

    bListItem.SetImageFromFile(AppPath & "\btnhome.bmp")
    bListItem.ImageLeft = 10
    bListItem.ImageHeight = 20
    bListItem.ImageWidth = 20
    bListItem.ImageTop = 10

 

I

IansResearch

Member

Licensed User

• Feb 3, 2010

• #4

Thank you both ... works great ... :sign0060:

But the transparency of the image shows up white on the HTC Touch HD while on the IDE under Windows Vista shows fine.

What is causing this?

 

M

mjcoon

Well-Known Member

Licensed User

• Feb 3, 2010

• #5

IansResearch said:

TBut the transparency of the image shows up white on the HTC Touch HD while on the IDE under Windows Vista shows fine.

What is causing this?

Click to expand...

I don't know much about the internals of the re-sizing process but I can guess...

If the transparency determination depends on the colour of a given single corner pixel, and the re-sizing process is averaging that pixel with adjacent ones, perhaps the corner pixel ends up a different colour. Then when calculating which pixels are transparent the answer would come out wrong.

Experimentally try extending the transparency pixel colour (if this is how it is being done) to the surrounding area? And/or reduce the number of colours?

Mike.

 

I

IansResearch

Member

Licensed User

• Feb 4, 2010

• #6

Is it possible that PNG (transparency) format is not supported on Windows Mobile 6.1 .NETCF2?

If that is true what format should I use with bList control ?

 

Erel

B4X founder

Staff member

Licensed User

Longtime User

• Feb 4, 2010

• #7

Is it possible that PNG (transparency) format is not supported on Windows Mobile 6.1 .NETCF2?

Click to expand...

Yes, .Net CF do not support PNG transparency.

You can use a solution like this one: http://www.b4x.com/forum/official-updates/4881-blist-v0-9-beta-released-5.html#post30871 and do all the drawing yourself and that includes on drawing transparent images (by explicitly defining the 'transparent' color).

 

I

IansResearch

Member

Licensed User

• Feb 4, 2010

• #8

Thanks Erel ... thats great...

I wonder could the next version of bList contain additional properties for the list items ImageTransparency (true or false), ImageTransparencyColor (RGB)

This just keeps it all neat. I am presuming that blist library draws the image.

Thank you for your help.

 

Last edited: Feb 4, 2010