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Alternate Selection Methods in Photoshop
version 5.5

There are many methods of making complex selections in Photoshop, such as the Marquee tool, the lasso, and the magic wand. However, I have found that sometimes I just don't like the quality I get from using those tools – I want a little more control.

While I was working on a freelance project which involved isolating a very complex sculpture from a non-uniform background (draped fabric), I had a thought. What if I could simply define the background colors as being transparent and get rid of the background that way, while keeping the smooth, anti-aliased and semitransparent edges that you get while using the normal selection tools?

Well, it can be done! This method won't work with every image, but it will work with many, and it saves a lot of time.

First, download this archived image of a daisy, or get the image here. Open it in Photoshop and resave it as a Photoshop file. We want to isolate the full daisy from the rest of the image.

1. Duplicate the image (Image> Duplicate). Close the original.

2. Change the color mode to Indexed (Image> Mode> Indexed Color). Set the number of colors to 100, and the dither to None. The color quality of this image is not very important (you'll see why in a minute).

3. We are going to create a transparent gif from this image (can you see where I am heading with this?). From the FILE menu, select Export > GIF89a. Uncheck the Interlaced box. Use the eyedropper tool to select the colors you'd like to have transparent. You can select just about all of the blues. Click the OK button and save your file.

4. Open the gif file you've just created. It should appear in Photoshop with a transparent background. We want to change the image back to RGB. (Image > Mode > RGB)

5. Once the image is in RGB, you can delete unnecessary parts of the image. Delete everything except the full daisy. You can use the rectangular marquee tool and the eraser set to pencil. We don’t want to use any tools that will cause anti-aliasing.

6. Command-click the image layer in the Layers Palette. This will select the image (and auto-shrink the borders to the image borders). You will want to use the marquee tool to add to the selection (little areas accidentally deleted when exporting.

7. Now we need to save the selection. Go to the Select menu and choose Save Selection…. Create a new channel. This will create a new channel named Alpha 1.

8. Go to the Channels Palette. Select Alpha 1. From the Select menu, Select All and copy the image.

9. Create a new file and paste the image. You will notice that the edges are a bit jagged. We need to clean those up a bit before we can use it.

10. First, we will run the Gaussian Blur filter set to 0.6 pixels.

11. Go to the Channels palette and command-click the Alpha 1 channel to load that selection.

12. Now, from the Select menu, choose Modify > Smooth. Set the value to 2.

13. Choose Inverse Selection from the Select menu. Fill with black (quick way - hit the D key to set the foreground and background colors to the default black and white, then Option-Delete to fill with the foreground color). This will refine the edges a bit more, but it is still not enough.

14. Deselect the image, then choose INVERT from the IMAGE menu.

15. Use the paintbrush at the second smallest size to further refine the edges. I have noticed that the anti-aliasing is a little off where the angle of the edge is fairly shallow.

16. Select All and copy.

17. Open the good copy of your image. Duplicate the layer (we want to keep an untouched layer in case of goofs), and hide the background layer.

18. In the Channels Palette, create a new channel. Paste the refined image into this channel.

19. From the SELECT menu, load the new channel. Select > Load Selection… Pick Alpha 1. The area around the daisy should be selected.

20. Delete the selection and deselect the image. You can clean up any edges that need it.

21. Place your new, isolated object over a flat color background to check for problem areas. You can also use the Unsharp Mask filter to sharpen things up a bit. For effect, you can add a drop shadow behind the image with a Gaussian blur of 2. 4 and no offset (works great over dark colors - very subtle).

Whew! I know it seems like a lot to do, and that using the lasso tool might be quicker (and for some things it will), but the more I use this technique, the faster it becomes. I could spend up to an hour on some selections and isolations using the regular tools – this cuts it down significantly.