Photo Editing Tutorial : Lasso, Transparency and Layers

The story so far….

Note – This is not the first post in this series relating to a photo editing tutorial.  If you haven’t already done so, please read the earlier post below:

In this first example, over the next couple of posts, we will be taking a photo of my arm holding and apple and changing the background to that of a beach.  In my case, I will be using Photoshop, but if you don’t have photo editing software, there are lots of free options out there, is just one of many.

Photo Editing Before and After

This post will look at 3 topics to start

  1. Layers
  2. Transparency
  3. Lasso


If you put  a post-it note on an A4 page, you will see a post-it on an A4 page.  Now, if you put an A4 page on a post-it you will see an A4 page only, because it is covering the post-it.

That is basically how layers work, you can move around parts of different images to put together one image from several.  In our project, my arm holding the apple is on one layer and the beach is on another layer.  The layer with my arm will be put on top of the beach layer.

In the image below, you will see a circle and square which overlap.  On the left, the circle layer is above the square layer, so you can see the circle overlapping the square.  On the right, the square layer is over the circle layer, so you can see the square overlapping the circle.

Photo Editing Layers Demonstration

The same theory applies to putting together different images or collages.  You move around layers to get the result you want.



To work with layers and putting together different images, one very important thing to watch out for is transparency!

When we undertake the project, one of the first things we’ll do will be delete the background around my arm and apple in the original image.  When we are doing this, you should hopefully see that after deleting part of the image, you see a checkered pattern.  This means that the background is transparent.

Photo  Editing Transparency

If we put this image as a layer over our beach image, you will see my arm on the beach image.  This is because when we deleted part of the first image, it left a transparent background.

However, if the background was white after deleting, this means that the background may be a solid color, white for example.  If I put this image on our beach layer, then you will see my arm and apple in a white box.  This would be no different than painting white around my arm and apple.  We need to see the transparent background on projects like this.

Note : In Photoshop, when I open an image, the image itself is a background layer.  If I delete part of the image it leaves a white background, not a transparent one.  To get around this, I create a new transparent layer, on top of the original image.  Then I duplicate my image layer and put that on top of my transparent layer.

I can now delete the bottom layer, which was my original background layer.  Now I can delete parts of my top layer which exposes the layer underneath (which is transparent).


Lasso Tool

There are usually two lasso options – freehand and polygonal.  In some cases, there may be a third (magnetic), but here I will look at the first 2.

The lasso tool lets you grab part of an image by drawing around it.  The selected area can then be copied and pasted to another image or transparent layer.

The icon for the lasso tool resembles a lasso (obviously)

Lasso Tool Icon


Freehand Lasso Tool

After selecting the Freehand Lasso, you can click and hold down the mouse button while you draw around the image section that you want.  When you release the mouse button, if you don’t draw back to where you started, the lasso tool will automatically close the loop between where you first clicked the mouse and where you released it.  Depending on your skill with a mouse, the image size and accuracy needed, this can be the quickest way to take part of an image.

In the example below, I used the Freehand Lasso tool to draw around my hand.  You can see the area highlighted by the Freehand Lasso tool.  I could have saved time by selecting my arm and apple only, but unfortunately I have a shaky hand which would not give me the accuracy I need to only highlight my arm and apple.  When I copy this to another layer, only the selected image is copied across.  This is a quick way to delete alot of the image that I do not want.

Photo Editing Freehand Lasso


 Polygonal Lasso Tool

The Polygonal Lasso tool allows you to select part of an image using straight lines.  Each click of the mouse creates a new point and the polygonal tool creates a line between where you click your mouse now and where you last clicked it.  This is the lasso tool that I use.  I set a series of points around the image I want to select (but not too close).

Photo Editing Polygonal Lasso Tool

In the above image you can see the selection is made up of a series of straight lines between points, each point is where I clicked my mouse when making the selection.


What’s Next?

At this point, we’ve covered most of the theory that you will need when next week we actually do some editing.

In the next post we will start removing the background from around my arm.


Next >>

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