Reusing alpha channels

I heard you can take the saved alpha channels from an article of clothing you have made and reuse them to save time. Anyone have an idea on how to do this. An answer would be greatly appreciated

Good question, Amia. Welcome to the forums, by the way.

If you're using Photoshop, an alpha channel, just like any other image element can be cut and pasted from one image to the next quite easily. Here are two really simple ways to do it:

Method 1 - Cut & Paste

1. On the Channels Palette, turn off visibility for the RGB channels and turn on visibility for the alpha channel. (Visibility is turned on and off by clicking the little eyeball symbol to the left of each channel's name) Now, select the alpha channel either by ctrl-clicking its thumbnail or by clicking on the button at the left most button at the bottom of the palette, the one that looks like a dotted circle, and says "Load Channel as Selection" when you hover your mouse over it. Now that you've got the channel selected, copy it to your OS clipboard by pressing ctrl-C or by going to the Edit Menu at the top of the screen, and clicking Edit -> Copy.
   
   
   
2. Now open your new image, go to the Channels Palette, and create a new channel by clicking the button at the bottom that looks like a square sticker being peeled from its backing. It will say "Create New Channel" when you hover you mouse over it. By default, the new channel will be called "Alpha 1". Once it's been created, simply paste from the clipboard by pressing ctrl-V or by going Edit -> Paste. You should now see the alpha channel looks just like the one in your first image.

Method 2 - Drag & Drop

1. Open both images and align them on your screen so you can see them both at the same time.
   
   
   
2. Go to the Channels Palette on the source image (by "source image", I mean the one that has the alpha channel in it that you want to copy), click on the name of the alpha channel, and then drag it onto the canvas in the other image. The secod image will now contain an exact copy of the first image's alpha channel.

Both of these methods take no more than a few seconds, and they'll work for all elements of the image, not just the alpha channel. You can copy layers, channels, selections, etc from one image to the next this way.

If you're using PSP, it's a little more round about since PSP doesn't allow direct access to channels. You have to load the alpha channel as a mask, copy the mask, apply it to the layer set in the new image, and finally, copy it to alpha using the procedure outlined in the transparency guide at the top of this forum.

If you're using GIMP, I'm sorry, I haven't had enough time to play with GIMP yet to be comfortable with it. It's a good program, but I really hate its interface, so I have a little trouble motivating myself to learn it well. Ive been resisting the temptation to install GIMPshop to make it better since I do want to learn its native structure first. I'll get to it sooner or later.

If there's anything here you didn't understand, come on back and ask. Good luck.

Assuming you're using Photoshop, you can go to the channels tab (next to the layer tab) and select the alpha channel. Then just cut and paste everything on it into the alpha channel in your new clothing file. But most likely you'd still have to reedit the alpha channel to suit the clothing shape.

I prefer to just reuse the same file and replace the clothing instead.

In version 1.2 of the GIMP, the easiest thing to do is to use a mask, instead of directly manipulating the alpha channel.

If you use a layer mask, it shows up as a separate image just to the right of the layer it is masking in the layer menu. If you select it you will be able to copy and paste in it just as you would with any other image.

Generally what I do is this:
1) Use the magic wand with the "threshold" set all the way up to select all non-transparent parts of the image.
2) Copy
3) Right-click the "cloth" layer, and add a mask.
4) Select the mask layer.
5) Fill the selection with white
6) Invert the selection, then fill with black.

Now you can copy and paste this mask to re-use it in any file.

Thanks, OneBigRiver, but how do you then copy the mask to the alpha channel? Every time I try, I end up with the mask as somethig seperate in the channels palette. The alpha channel itself seems always to only want to operate as WYSIWYG, and that's problematic because of haloing. Surely there's got to be a way to paste the mask into the channel without having to have the mask itself actually be visible. How is this done?

Which version of Gimp are you using? I think that 1.2 (I use 1.2.5) and 2.x do transparency differently. I'm not sure I 100% understand your question, but let me see if I can figure it out...

A "layer mask" is simply a grayscale image that tells the layer "don't draw this part of the layer." For whatever reason, 1.x versions of GIMP do not allow direct manipulation of the alpha channel through the "channels" tab. ( http://www.users.muohio.edu/brinkmwj/pictures/SecondLife/sl2.tiff ) Here is a picture that shows this weird behavior: Clearly there IS an alpha channel, but the GIMP does not think of it this way. So if you just use the eraser, you can affect the alpha channel, but you run into all kinds of issues: I particularly hate the fact that I often make a boo-boo and destroy my texture.

Instead, we ( http://www.users.muohio.edu/brinkmwj/pictures/SecondLife/sl3.tiff )add a layer mask</a>. I usually choose to make it white (fully opaque), and then delete wherever I want to make a hole.

Now, in the layer panel, I select the mask, not the image itself, for modification. For example, in ( http://www.users.muohio.edu/brinkmwj/pictures/SecondLife/sl4.tiff ) this image I am cutting a square hole in the middle. I did this by selecting the rectangle that I wanted to cut out, and then fillling it with black. Notice the cool thing that happened: From the Layer menu you can see that I didn't modify the color info of the layer at all! Only the alpha channel was modified, as displayed by the layer's mask.

Using this technique you should not get "haloing" in the traditional sense: The really nasty form of haloing generally only happens if you have something that is supposed to be partially transparent, but the image file (or the file-saving code used by your paint program) does not support partial transparency.

One thing that people sometimes see is anti-aliasing. If you have anti-alias or feather set for your tools when you are modifying the layer mask, then you are not going to get nice crisp holes: You will get some blend from transparent to opaque (like http://www.users.muohio.edu/brinkmwj/pictures/SecondLife/sl5.tiff ).

I hope this helps some... Gimp 1.2.x, while powerful and well documented, has a few strange behaviors, and this weird treatment of alpha is a bit annoying. If you get comfortable thinking of the layer mask as "the alpha channel," and take care not to modify alpha directly using the eraser or "clear," things work out pretty okay.

I just want to thank you guys soooooo much for responding to my post. You do not know how much you guys are appreciated