lesson : photoshop elements – first stepswebs.wofford.edu/whisnantdm/training/gimp/gimp 06...

Lesson 6 GIMP – Layers July 14, 2010

David Whisnant

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GIMP – Layers

One of the most powerful features of modern imaging software is the ability to work with layers.

If an image is made of layers, we can work on the part that is in one layer without affecting the

others. This is best understood by creating an image made of more than one layer.

Creating a Blank Image

Make sure that the background color is white. If it is not, change it to white.

Select File, New from the main menu.

Create a 1024 x 768 image and save it with

the name Composite.xcf


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Creating a Composite Image

Open Grief.jpg and save as Grief.xcf.

You will now have two GIMP windows open,

one containing Composite.xcf and one

containing Grief.xcf.

Our goal now is to combine the two images.

In the “Grief” image, use the Selection tools and Eraser tool to delete out the

section of the picture that is not occupied by the figure.

The Fuzzy Select Tool

A useful selection tool we did not cover in the preceding lesson is the Fuzzy

Select Tool, which selects contiguous regions that are of the same color. Choose

this tool.

Set the Threshold for the tool to a low number, say 1.0. The

size of the threshold determines how similar the colors are that

will be selected by the tool. A threshold of 1.0

means that the tool will only select identical colors.

Make sure Feather edges is checked

Click on the white area of the picture with the selection tool.

This will select all contiguous pixels that are white. You

should see that the outer area you have deleted is selected.


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Inverting a Selection

We really want to select the figure herself, not the outer white area. To do this,

choose Select, Invert from the main menu.

This will reverse the selection so that the figure rather than its white

surroundings are selected.

Use Edit, Copy to copy the selected figure.

Creating a New Layer

Go back to the Composite.xcf picture and

select Layer, New from the main menu. Then

click on OK in the dialog box that appears.

This creates a transparent floating layer on top

of the original white image, a little like a sheet

of glass.

You can tell the layer is there on the Layers, etc information

window. If you click on the Layers icon, you will see that the image

now consists of a background (in this case white) and a new layer.

In the Layers, etc. information window, select the New Layer.


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Use Edit, Paste from the main menu to paste the

copy of the figure in Composite.xcf. It will

become a third layer for a moment, floating above

the transparent layer you just created.

Move the figure layer so that the figure is in the

lower left corner of the image. When you click

away from the figure, its layer will be incorporated

with the transparent layer you created a moment

ago.

The image now has two layers:

The white background

The layer containing the figure.

The checkerboard pattern in the New Layer

indicates that this portion of the layer is

transparent.


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The Eraser Tool

You might notice that the right edge of the cloak in the figure is vertical and looks unnatural. We

need to correct this,

Select the Eraser tool.

Configure the Eraser tool as a Fuzzy Circle with a Scale of around 1.25.

Select the upper layer that

contains the figure. Use the

eraser took to remove a

little of the cloak to give a

smooth and irregular edge.

NOTE: If the Eraser tool

does not appear to work,

you probably have the

Background layer selected

rather than Layer 1.


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Creating a Layer with a Color Gradient

Let’s create another layer between the two layers we have.

Select the Background layer and then create a New layer.

You now should have three layers.

Select the middle layer (the one you just created).

Change the foreground color to a shade of blue.

Choose the Gradient Tool in the Toolbox.


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Click the mouse at the top of the picture and, holding the mouse

button down, drag the cursor down to the lower part of the screen.

You should see a line follow the cursor. When you release the mouse

button, you will see a blue gradient painted on the middle layer,

behind the figure.

Viewing or Hiding Layers

You can hide or show a layer by clicking on its eye icon

in the layer palette. If the eye is not visible, then the

layer will be hidden on the screen. If the eye is visible,

then the layer will be shown on the screen.

Try this with one or more of the layers and watch what

you see on the screen.

When you are through, make sure all the layers are

visible.


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Layer Opacity

Select Layer 1, which contains the figure.

In the upper right of the Layers palette, you will see an Opacity slider, which controls how

much of underlying layers will show through a selected layer.

Opacity = 100% means a layer is completely opaque so nothing in a lower layer will

show.

Opacity = 0% means a layer is completely transparent and no longer visible.

Change the Opacity of Layer 1 to 50%, which means that it will be 50%

transparent.

The figure now is slightly obscured by the gradient

layer, which is showing through from below.


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Adding Text Layers to an Image

Choose the Text tool with a Vivaldi Italic Condensed font.

Select 80 px as the text size.

The Anti-aliased button should be on. Anti-aliasing fills in the edge

pixels on type to make the edges smoother.

Set the Text Color to white.

Click on the editing screen somewhere

near the figure. You will see a GIMP

Text Editor dialog box appear. Type

“Adams Memorial” in the GIMP Text

Editor

As you type the words in the Text

Editor, you will see them appear on the

editing screen

If the “Layers. Etc.” dock is not open,

open it.


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Select the text layer and

move it approximately to

the position shown in the

picture at the right.

Drop Shadows

We can add drop shadows to the text to make it stand out from the

background. Select the text layer.

Choose Filters, Light and Shadow, Drop Shadow

from the main menu.

Specify the properties

of the drop shadow and

click on OK.


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Arranging the Order of Layers

You can change the order of

layers from the Layers menu.

Select New Layer #1, which

contains the blue background

Choose Layer, Stack, Raise Layer in the main menu.

What happens to the image when you do this?

Look at the Layers palette. Has the figure really disappeared? Why can’t you see it?

Undo the change.

Deleting Layers

You can delete a layer by selecting it an pressing the Delete on the keyboard.

Try it with one of the layers.

Undo the change.

Merging Visible Layers

Layers give GIMP a lot to remember and can lead to large file sizes. If you are

absolutely sure you are finished with an image, you may want to merge the

layers into one image. If you have any doubt about needing the layers later, it

would be a good idea to save the image under another name after merging.

Choose Image, Merge Visible Layers from the main menu. What does this

do?

Undo the change


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You also may want to merge only some of the layers in a stack,

rather than all of them. For example, you may want to merge the

bottom three layers (background, blue color, figure) but leave

the test floating on top.

Click on the eye icon for the two layers you do not want to

merge. You will see that the text and the drop shadow disappear

from the image because they no longer are visible.

Next choose Image, Merge Visible Layers from the main

menu. This will merge the visible layers into one layer, but leave

the invisible layers unaffected.

Correcting Perspective Problems

Open the file Chicago.jpg.

If you take a picture of a building from

ground level with a wide-angle lens, the

buildings appear to lean toward the center.

This is particularly apparent if you view the

grid, as shown in the picture at the right.

You may want to improve the look of the

image by straightening the buildings.

View the grid as we did when you rotated the image in the first lesson


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Select Tools, Transform Tools, Perspective

You will see small squares at the four

corners of the image.

Push the lower squares in and pull the upper

squares out until the straight lines in the

image line up with the vertical lines in the

grid.

Click on Transform in the Perspective dialog box.

The image will be transformed to straighten the

perspective in the image. This will leave some

blank spaces at the bottom of the image, which

will need to be cropped.

You may need to sharpen the image a little with

the Unsharp Mask following the

transformation.


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Practice Problems

1. Using Ben.jpg and Old_MainSpring.jpg, make

this image shown here.

2. Open Street.jpg and make the following adjustments.

Correct its perspective

Sharpen the image

Increase the saturation of the image slightly to give it more

punch

3. Make adjustments to the scanned image, SantAntimo.jpg. Include

the following adjustments.

Correct its perspective

Remove dust and people that are in the picture.

Sharpen the image


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4. Open Famille.jpg and make the following

adjustments.

Brighten the shadows without

changing the properly exposed sky.

This may not take much adjustment to

look OK.

Adjust the perspective

Change the saturation if necessary.

Sharpen the image

Crop the image to remove the

telephone pole at the right.

lesson : photoshop elements – first stepswebs.wofford.edu/whisnantdm/training/gimp/gimp 06...

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