Tree texture alpha channel issue

I'm having an issue with tree textures for the Guam PGUM scenery by Bill Melichar, available here guam04.zip. Some tree textures don't have alpha channels so you wind up with a black rectangular box with the image of the tree inside it. I know one cure for this is to use DXTBmp and create and save an alpha channel for those textures. However, a few of the textures i cannot create an alpha channel for, for example texture CocoPalm_shortWide.bmp. The alpha channel just stays white. I'm assuming that maybe the black in that texture file is not pure black? Is there a way to make the alpha channel without doing a lot of editing to the bmp? Or is there another program that will make the alpha channel that works better than DXTBmp? I guess I could find another palm tree with a good alpha and make a copy of it and then just rename it to CocoPalm_shortWide.bmp? Thx for any help. I'm also having this issue with some trees at PHNL, which is another Bill Melichar airport file available here. Funny, I've used these sceneries for quite a long time now and didn't have issues, but that was on older laptops with different vid cards and OS, I don't know why that would make a difference, but something has made a difference. Running windows 10 now with Nvidia Geforce GTC 1050Ti.

I'm no expert but have you updated your video drivers, but before you do backup the originals?

 

Col.

Yes, video drivers are up to date. Upon further experimenting I found that the trees for Honolulu were actually from a scenery for Hickam AFB I think by DBWsim available here which complemented PHNL. Those trees had a olive green background and I was able to make alpha channel using "create alpha from color" and I was able to match up the color and make the alpha. It would not create an alpha using the "Create alpha channel(green)" option. However I was not able to use that same technique with the trees from Guam. However, answering my own question in the original post, I just found another palm tree that had a good alpha, renamed it to CocoPalm_shortWide.bmp and all is well. You lose a little tree diversity doing that, but oh well, better than trees surrounded by a black rectangle.

Great! Glad you got sorted, it's nice when you do that and solve it yourself if you get my meaning, I ask when I don't know but sometimes I play around and find the answer.

 

Col.