Saving to an Alpha Channel

[bighop]

Hello All,

 

I've been trying to save an image with an Alpha channel, bring it into AM and loose the black background. I think I finally did it.

 

I created a set of directions, so far this process has worked for me. If anyone knows of an easier method, please let me know.

 

Andy

leaf.mov

Alpha_channel_directions.pdf

[c-wheeler]

Works for me! Thanks for going to the trouble of posting a tute sheet.

 

Chris

[bighop]

Your welcome.

[johnl3d]

Not sure why you had a lot of extra steps but after selecting the image of the leaf ..open channels menu chosse new channel fill in leave outline with white alpha is done save .

 

 

At least this is the way I usually do it

 

Also when you have the leaf shape selected you can select path menu make work path and then export the path as illustrator file. New model in am use ai wizard and you can get leaf model...sometime if shape is too complex it might not be the best

 

Your tut is probably easier to follow than mine.

[bighop]

I tried that, but with the alpha white, and nothing in the selection, it wouldn't work for me. Also, if the Alpha was gray, I was getting a trasparent image.

 

I would like to cut down the steps somehow.

[Fuchur]

I tried that, but with the alpha white, and nothing in the selection, it wouldn't work for me. Also, if the Alpha was gray, I was getting a trasparent image.

 

I would like to cut down the steps somehow.

 

I assume you are using photoshop:

 

1.) Load your image of the leaf.

2.) Doubleclick on the Background-Layer to make it manipulatable (so you can delete the not needed background and make the layers background transparent in photoshop. It is easier to manipulate and select your leaf that way).

3.) Select the leaf for example by using the lasso-tool or the magic wand.

4.) Go to "Selection -> Save Selection".

5.) "Name" is for example Alpha. Leave the remaining things like they are.

6.) Save your image as a TGA with 32bit (->important).

 

You can look at your Channels-window (another tab near the layer-window if you activated it under "window") to see the alpha. It should be white where the leaf is and black where the background is /was.

This can be done manuel too, by creating in the channel-window a new channel, make the other channels (R G B RGB) all invisible. Now you can paint directly on the alpha-channel. White means fully visible, black means not visible. Greys inbetween are transparency-values.

 

If you have many pictures of a leaf you want to manipulate this way you can try to use the macros of Photoshop for a faster access.

Macros are predefined steps which will be performed by Photoshop on several different images.

 

In the end you have to hit a "record"-button before you do the steps above. After that you can just stop the record and apply it as a macro on every picture you want. It will only be practicable with a leaf which has a huge differnz in color to the background and if you use the magic wand-tool. The macro can only work with images which behave the same way on the same comment.

 

*Fuchur*

 

PS: Another possibility is to use png-images(24 bit) instead of TGAs. You dont have to assign an alpha-channel here. Just make the background transparent in Photoshop and save as a PNG with transparency.

I think A:M v12 or something like that first introduce the import of png-images.

[bighop]

Ok,

 

That works! Thank you. I have to change my directions. My only concerns....

 

1. I have to draw, or start doing another procedure for the transparency to take effect in AM. (I'm on a Mac, so I don't know if that is a mac issue.

 

2. If i have any sections of my grid that DOES NOT contain the decal, I have to delete them, or it just shows up white.

 

3. I have been saving as 32 bit, but why is it important?

 

Thanks for this, I'll post new directions later today.

 

Andy

[NancyGormezano]

2. If i have any sections of my grid that DOES NOT contain the decal, I have to delete them, or it just shows up white.

 

Correct

 

3. I have been saving as 32 bit, but why is it important?

 

Normally images are saved in 24 bit (just rgb data - 8 bits per channel) - the extra 8 bits (32) is for the alpha channel data. If you don't save in 32 bit - you don't get the alpha channel.

[Fuchur]

As Nancy already told you:

 

0-255 are the grey-values between black and white. So you need 256 different possibilities to save these informations.

2^8 => 256 -> so you need 8 bit. This would be a greyvalue-image.

 

To get an RGB-images you need 3 Channels (red, green, blue) -> 3 * 8 bit = 24 Bit.

To get transparency to work you need another grey-channel which will handle that.

White areas will be solid, black areas will be transparent.

-> another 8 bit...

 

= 32 bit...

 

And now ask me why a PNG-images with only 24 bit can provide Color and Transparency... I dont know neighter

(Anyone knows about that?)

 

*Fuchur*

[bighop]

I like the 6 steps vs the 13 steps I did...thanks again.

 

Here is an updated tutorial.

New_Alpha_Directions.pdf

[rusty]

What I do is:

 

1. click on the layer (selects all pixels on layer)

2. Do Selection->Save Selection name it 'alpha'

3. Save as 32 bit targa (tga)

 

Looking closer, I think you've already been whittled down to this with some extra safety stuff and 'looking'.

 

Rusty