I have an image (a logo) that was on a black background.
I have used Photoshop's (CS5) Background Eraser Tool to remove the background.
This is great except that there are black (well grey/black) dots around the image on the curves.
How can I remove them?
You can use the Mask tool (press q), then brush all the area which you want to remove (pressing q again), and finally press Delete.
When you get the logo alone paste it into a new file with a white background and then brush or delete those black dots, zoom it to the maximum for pixel perfection. I do the same when I have to work on small things.
You can also zoom in and use the erasertool, be sure to zoom in so you won't forget any pixels.
You can use the magnetic lasso tool (or regular lasso tool) to crudely select the logo. Then, invert the selection (Selection>Invert), and hit the Del key.
Alternatively, you can select the background with the magic wand tool and delete it(I will talk about an effect to erase all the little dots later)
If you used the lasso tool, then use the magic wand tool to select the black background and hit Del
You can optionally use the eraser tool close to the edge, but it's not really necessarily because the what I talk about next should get rid of the edge. If you want to make sure you dont erase the logo at all, use the magic wand tool to select the transparent area, and then use the regular lasso with Shift to add all the little dots. It should go fast if you use large circles to add all the dots.
Whatever tool you used, you will probably need to remove the jagged edges and little gray dots it left behind.
You can select the transparent area with the magic wand tool and then select inverse
then create a new mask (below all your layers rectangle with a dot in the center)
then go to filter->blur->gausian blur and adjust the value until your jagged edge is highlighted (around 2.0 is ussually enough. Make sure you have the mask selected and not your regular layer otherwise it wont work )
Click OK and then go to image->adjustments->levels and play around with the sliders on the top (the one that has 3 sliders with the gray one in the middle)
Move the sliders beginning with the left one until the jagged edges are gone. Then move the the right one until the whole image is visible.
The jagged edges should now be gone and so should the background...
You can also use the eraser tool and make it really large with the ] key, then click on the edges, and then start using the magic wand tool .
Select everything but the logo using the wand tool.
Create a new layer (Layer 2).
Fill in the selection with black (or whatever) on Layer 2.
Select everything in Layer 2 (Ctrl+A), and shrink it down by a few pixels. (Hold Ctrl to get an "even" shrink, and use the dots at the corners of the selection to shrink it. I think it's Ctrl, but this may be different in Photoshop from my other editors.)
Select the black portion (using the wand tool) of Layer 2.
Invert selection.
Go to Layer 1, and press "delete".
Delete Layer 2.
If you still have the original image, can you post it? It may be easier to delete the background than you think. (No eraser tool required. Eraser tools are for beginners. ;) )
Those answers are all pretty long ways to achieve your goal. An easier way is to simply command-click on the layer thumbnail to select the object/shape, then go to Select > Modify > Contract then contract the selection by a pixel or two, depending on your needs. Next step is to hit command+I to invert the selection then hit the delete key.
Use the layers black value as the layermask. This method requires no tracing and is also non-destructable:
I got a video that shows how to completely remove the background from an image
How to crop a image in any shape by removing its canvas background
double clik on the background layer to unlock him.. so you convert the background to a normal layer wich support the transparency .. then do what others say above ..
