Monday, July 26, 2010

Creating, Adding, Subtracting, and Intersecting Selections

With the Marquee tools, you have several options. You can create new selections, add to or subtract from already created selections, or create a selection from an area where two selections intersect.
The following list summarizes the use of these options. You’ll get some hands-on experience with these options in a moment.

  • New Selection: This is the default option whenever you select and use a Marquee tool.

  • Add to Selection: This option allows you to add more selections to an existing selection. You can also hold the Shift key to add selections on the fly (without pressing the Add to Selection button from the options bar).

  • Subtract from Selection: This option is similar to Add to Selection; however, instead of adding to an existing selection, this option subtracts from existing selections. You can also hold the Alt key to subtract selections on the fly (without pressing the Subtract from Selection button from the options bar).

  • Intersect with Selection: This option allows you to create a selection based on the area where two selections intersect.
We’ll look at using these selection options in a moment.

Using the Feather Option

You may have seen the softened edges around images — where edges of an image gradually fade to transparent. In Photoshop, this is known as feathering.
You can add this effect by using the Feather option with your selections. When you select one of the Marquee tools, you’ll notice the Feather text box on the options bar. This text box sits next to the Intersect with Selection button, and is shown in figure below.
For the examples in this tutorial, we want to soften the edges of our selection. You can do this by entering a number in the Feather text box. A large number will create a wide range of transition from your image to transparency. A small number will create a small faded edge around your image.
Perform the following before moving on:

  1. Change the Feather text box value to 20 px.

The Anti-alias Option

Next to the Feather text box is the Anti-alias option. Anti-aliasing is Photoshop’s method of smoothing the jagged appearance of angled and curved lines. Photoshop does this by surrounding the pixels with intermediate shades of the line, as well as manipulating the size and horizontal alignment of pixels. Figure below displays the difference between normal and anti-aliased ellipses.

Unless you’re going for the “pixelated-choppy” look, always keep the Anti-alias check box checked with your selections. This will ensure that any shapes you create or combine with other images will have the smoothest edges possible.
Perform the following before moving on:

  1. Check the Anti-alias check box, as shown in figure below.

The Style Option

Photoshop’s Style options allow you to constrain selections as they’re created. There are three Style options you can use with selections. It’s usually a good idea to keep the Normal style selected; however, there are other style options available that might serve your purposes at some later date.

  • Normal: There’s no constraint with your selection. In other words, you can draw a selection any size you want. Most of the time, you’ll want to keep your selection style set to Normal.

  • Fixed Aspect Ratio: This option allows you to define the ratio of the selection. For example, say you wanted to create a perfect circle selection. You could do one of two things:

    1. Hold the Alt key while the Style option is set to Normal. This allows you to create a selection with a 1 to 1 ratio (for example, you’ll create a perfect square or a perfect circle).

    2. Select the Fixed Aspect Ratio style option. You can then enter a numerical value in the Width and Height text fields beside the Style drop-down field. For example, entering a 1 in the Width text field and a 1 in the Height text field allows you to create a perfect square or a perfect circle.

  • Fixed Size: This option, similar to the Fixed Aspect Ratio option, allows you to define the size of the selection. Next to the Style drop-down field, there are Width and Height text fields. You can enter the width and height of the selection within these fields.
Perform the following before moving on:

  1. Set the Style option to Normal, as shown in figure below.

Now that you’ve set some of your selection options, let’s put them to work.

Separating a Part of an Image

  1. Select the World.jpg image (if it’s not already selected). Then, create a selection around the continents with the Elliptical Marquee tool. Press the New Selection button on the options bar when you do this.
    Your image should look something like figure below.

    Then perform the following to combine this image with the new, blank image you created earlier in this tutorial.

  2. Arrange the Photoshop work area so you can see both World.jpg and the new, blank image.

  3. With the World.jpg image selected, go to the toolbox. Select the Move tool (found to the right of the Marquee tools). Then click and hold somewhere within the elliptical selection.

  4. Drag the elliptical selection onto the new, blank image, as shown in figure below.

For now, place the world selection at the upper-right side of the new, blank image. Notice the faded edges. This occurred because you set the selection’s Feather option to 20 px.

Cropping an Image

Another useful Selection tool is Photoshop’s Crop tool. This tool allows you to remove unwanted parts of an image quickly and easily.
To get an idea of how the Crop tool works, follow these steps:

  1. Make Bing_Building.jpg from your work area active.

  2. Select the Crop tool (the third icon on the left side of the toolbox).

  3. Use your mouse to draw a box around the area you wish to crop, as shown in figure below. 

    Notice the small, clear boxes found at the corners and in the center of the sides of the crop selection. You can drag any of these crop handles to resize your crop area. The area within the crop selection will remain. Areas outside the crop selection represent areas Photoshop will remove.

  4. Press the Enter key to crop the image. You image should look similar to figure below.

Crop Tool Options

Like most tools available from Photoshop’s toolbox, the Crop tool contains options (available from the options bar). With the Crop tool, there are two sets of options: those available before cropping and those available after cropping.
Crop Tool Options (Available before Cropping)
Select the Crop tool again, but don’t use it to draw your cropped selection just yet. Take a look at the options bar. It should look like figure below.

The Crop tool options (available before cropping) include:

  • Width: The Width box allows you to define exactly the width measurement of the crop selection.

  • Height: The Height box allows you to define exactly the height measurement of the crop selection.

  • Resolution: The Resolution box allows you to define the resolution of the crop selection. Since you’re cropping images for the web, you don’t want to make the resolution more than 72 ppi (pixels per inch). However, if you’re cropping images for print or some other media and want a crisp graphic, you might want to bump up the resolution of the image here.

  • Front Image: This button fills the Width, Height, and Resolutions boxes with the width, height, and resolution of the currently selected image window. This is useful if you want to make a cropped image the same size as another particular image.

  • Clear: This button removes any values in the Width, Height, and Resolution boxes.
Although you may find these options useful, personally I don’t use them a whole lot. I find it easier just to create the crop selection and define its size manually with the crop handles. But it’s a preference thing. Feel free to use these options and see how they feel to you.
Crop Tool Options (Available after Cropping)
With the Crop tool selected, let’s tweak our Bing_Building.jpg graphic. Select the Crop tool and use it to draw around the building image. Take a look at the options bar. It should look like figure below.

The Crop tool options (available after cropping) include:

  • Shield: The “shield” is the gray area outside the crop region. Photoshop selects the Shield check box by default. When you check the Shield check box, Photoshop grays out the areas that it will crop away. Unchecking the Shield check box removes the grayed-out effect.

  • Color: This option allows you to define the color of the cropped-out area.

  • Opacity: The Opacity option allows you to define the darkness of the shield color. The lighter the opacity, the more transparent the shield color. A shield color of 100% is pure black.

  • Perspective: This check box allows you to orient the crop selection. Often the horizon (or perspective) becomes skewed — sometimes purposely by the photographer for dramatic effect. The Perspective check box allows you to rotate your crop selection to fix perspective problems.
Of all these options, the most useful is the Perspective check box. Let’s demonstrate its use with the Bing_Building.jpg file. Notice the perspective of the building appears from below the horizon line. You can correct this with the Perspective option. Try the following:

  1. Select the Bing_Building.jpg image. Select the Crop tool and create a crop selection around the building.

  2. Check the Perspective check box in the options bar.

  3. Click and hold the crop handles. Notice now that you can move the individual crop handles, thus changing a single edge of the crop selection. Work your way around the crop handles, changing the crop selection so the boundaries are parallel to the building’s sides, as shown in figure below.

  4. Press the Enter key. Notice that Photoshop has now adjusted the perspective. The building sits straight now, rather than at an angle, as shown in figure below.

Let’s finish this activity by adding the building image to the image we started earlier in this tutorial.

  1. Select the Bing_Building.jpg image.

  2. Select the Rectangular Marquee tool.

  3. Set the Feather option to 20 px.

  4. Draw a rectangle around your building and drag it onto the image you started earlier in the tutorial that contains the elliptical selection from the World.jpg file. Your work area should look something like figure below.

    Open the Layers palette (if it’s not already open). Notice that every time you drag a new layer onto the blank image, a new layer is created. There should be a Background layer, a Layer 1 (which contains the map image), and a Layer 2 (which contains the building image). You can rename any of these layers with a more descriptive title.

Creating Irregular Selections with the Lasso Tools

You’ve looked at the Marquee tools and the Crop tool to create selections. But what about creating irregular selections? Take a look at the Bing_Profile.jpg image. Say you wanted to separate Mr. Bing from the image’s background. That’s difficult (if not impossible) to do with the Marquee tools or the Crop tool.
You have a couple of choices for creating irregular selections. You can use the Lasso tools (which we’ll cover in this tutorial) or you can use the Pen tool.

The Pen tool is one of Photoshop’s most useful tools. You’ll learn about the Pen tool in next tutorial.
Let’s take a look at the different Lasso tools (displayed in figure below) that can help you create unique selections.

The Lasso tools consist of the following:

  • Lasso Tool: This tool allows you to draw selections freehand with your mouse.

  • Polygonal Lasso Tool: This tool allows you to make selections by drawing straight lines, resulting in a polygonal shape.

  • Magnetic Lasso Tool: The easiest of the Lasso tools to use, this tool is similar to the Polygonal Lasso tool. The Magnetic Lasso tool attaches itself to the image (as if the image were magnetic). You’ll use this tool to separate the picture of Mr. Bing from the Bing_Profile.jpg image.
Select the Bing_Profile.jpg image. Then perform the following:

  1. Select the Magnetic Lasso tool from the toolbox.

  2. Before starting, notice the options bar. It’s similar to the options bar found with the Marquee tools. Change the Feather option to 20 px.

  3. Click on the image — maybe somewhere around the right side of the image (around Mr. Bing’s left hand).

  4. Left-click often to improve the Magnetic Lasso’s accuracy. Clicking creates points, represented by small boxes.

  5. If you need to restart, press the Esc key to remove the selection and start again.

  6. It might take a little practice. Work with the Magnetic Lasso tool until your result looks something like figure below. 

    Once you work your way around the image, it becomes a selection. If you’re having trouble creating a good selection with the Magnetic Lasso tool, you can fine-tune some of its options, which are shown in figure below.

    • Width: This option defines the edge distances (from the Magnetic Lasso’s center point) from which the Magnetic Lasso will try to attach.

    • Edge Contrast: This option defines the sensitivity of the Magnetic Lasso. The more sensitive the Magnetic Lasso, the more easily it attaches to the edges of a shape.

    • Frequency: This option defines how often the Magnetic Lasso creates anchor points along the selection path. You can also create these anchor points by left-clicking. The more anchor points you use, the more accurate the Magnetic Lasso’s selection will be.

    • Pen Pressure: This button enables the use of a pressure-sensitive tablet device to change the Magnetic Lasso’s selection width (similar to the Width option).

  7. Once you’re happy with your selection, drag it onto the new combined image created in this tutorial, as shown in figure below.

  8. Save this file as Bing_titlebar.psd.

    When you drag the Bing_Profile.jpg selection onto the new image, you may notice that it’s too large. You can shrink it down using Photoshop’s Transform feature. Press Ctrl+T. A Transform box surrounds the Mr. Bing selection. Hold the Shift key and grab one of the points on the Transform box. This allows you to resize the image while maintaining its dimensions.
In this tutorial:
  1. Combining Images
  2. Removing and Combining Parts of Images
  3. Creating, Adding, Subtracting and Intersecting Selection

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