Android Question Create a transparent JPG files with white background

klaus

Expert

Licensed User

Longtime User

• Dec 30, 2016

• #2

JPEG doesn't suppost transparency!
You should use PNG.
Instead of
C.DrawRect(Rect1, Colors.ARGB(0,255,255,255), True, 100dip)
use
C.DrawRect(Rect1, Colors.Transparent, True, 100dip)

 

Upvote 0

AlpVir

Well-Known Member

Licensed User

Longtime User

• Dec 30, 2016

• #3

It's true ! I had missed.
Thank you very much

 

Upvote 0

AlpVir

Well-Known Member

Licensed User

Longtime User

• Dec 30, 2016

• #4

However I checked just now that Photoshop can create JPG files with transparency !!!
What she explains ???
Is Android the responsible?

 

Upvote 0

klaus

Expert

Licensed User

Longtime User

• Dec 30, 2016

• #5

I don't know, I had in mind that JPEG doesn't support transparency, and checked shortly on internet before posting.

 

Upvote 0

JordiCP

Expert

Licensed User

Longtime User

• Dec 30, 2016

• #6

AlpVir said:

However I checked just now that Photoshop can create JPG files with transparency !!!

Click to expand...

I also thought it was impossible...have googled for it
If you are refering to JPEG 2000 (.jp2 or .jpx, but not .jpg or .jpeg) yes it allows transparency, but it "seems" that it is not widely supported (yet?)

 

Upvote 0

AlpVir

Well-Known Member

Licensed User

Longtime User

• Dec 31, 2016

• #7

With Photoshop in no time you can create an image with transparencies. Possible that you can not do the same with B4A ?
I attach a JPG image created with Photoshop and a PNG with transparent background, just as I want.

 

Attachments

• PNG.png

  13.3 KB · Views: 312
• Transparent.jpg

  26.8 KB · Views: 290

Upvote 0

JordiCP

Expert

Licensed User

Longtime User

• Jan 1, 2017

• #8

I can't see any transparency in your "Transparent.jpg" file --> does it have alpha channel?.

Not sure to understand exactly which is your concern

• If you want to create transparent images with B4A in no time --> as Klaus said save them as PNG

B4X:

Dim C As Canvas
Dim Rect1 As Rect
Dim BMPM As Bitmap 
BMPM.InitializeMutable(W,H)
C.Initialize2 (BMPM)
Rect1.Initialize(0,0,W-1,H-1)
C.DrawRect(Rect1,Colors.Transparent,True,100dip) 
C.DrawText("Happy 2017", 0, 0,Typeface.DEFAULT,20,Colors.Green,"LEFT")
Dim Out As OutputStream
Out = File.OpenOutput (File.DirRootExternal , "test.png",False )
C.Bitmap.WriteToStream (Out,100,"PNG")
Out.Close

 

Upvote 0

AlpVir

Well-Known Member

Licensed User

Longtime User

• Jan 1, 2017

• #9

After extensive research I concluded that (as I was told in this forum) JPG format does not support transparency !
Evidently with Photoshop you can create pseudo-transparency as I have shown in a picture attached to the post # 7. This led me into error in thinking that it could create JPG images with transparent backgrounds.
Thanks to all of the support

 

Upvote 0