Lasso tool: select only visible pixels

Question

Give a layer with some brush drawings, I want to use the lasso tool to select some parts of my drawing. However, I want the selection to only contain visible pixels. As it is now, the lasso tool's selection will contain the entire selection, regardless of there being transparent or visible pixels. Is this possible?

Look at this drawing: I have two layers. One is the background and another is the black circle.

Now I want to use the lasso tool to select this particular section of the circle:

But, as you can see, there are transparent pixels selected. What I want is something like this:

In other words, I want the selection area to only make use of pixels that are visible... Using the lasso tool.

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Since you insist on asking me why I want to achieve this, it is because I have a drawing I want to shade using gradients on specific parts. For example, I want to shade half of the left leg of this character:

So I use the lasso tool. But if I apply the gradient, it will also fill the area outside her leg.

I am aware that I could make a mask of her body so that the gradient will not overflow outside her leg. However, given my workflow, it would be a lot more efficient and easy if I could just configure the lasso tool to only grab visible pixels. This is the reason I want to achieve this: for efficiency/commodity.

Photoshop CC 2014, Mac OSX.

Answer 1

Do this:

1. Make selection
2. Right click on layer thumbnail and choose Intersect Transparency Mask

Image 1: Animation of intersecting the selection with transparency mask

Answer 2

There are many ways to alter a layer with transparency without altering the transparency.....

Which one you use depends upon your desired result and workflow.

1. Clipping Masks:
   

2. Command/Ctrl-Clicking the layer thumbnail to load it as a selection, then using a new layer:
   
   This method only selects the non-transparent pixels.

3. A layer mask on a new layer:
   

4. Layer Styles:
   

I think the least efficient way is #2 -- using selections.

Also be aware if you create a selection which contains transparent areas copying, duplicating, transforming, etc all ignore the transparent pixels. It is only when you attempt to fill a selection that any transparency may be covered depending upon your selection method.

Answer 3

So I stumbled upon this post with the same exact question, and I figured out another way while trying the other answers.

Here's what you do:

1. Make your selection any way you want; marquee, lasso, whatever.
2. Switch to the move tool (v)
3. Move your selection with the arrow keys any direction.

Your selection will refine to exclude transparent pixels! Yay!