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Chapter 4. Pixel Basics > Changing the canvas

Changing the canvas

The Canvas Size command changes the live, editable image area.

Note: If you want to enlarge the canvas area manually, right on the image, use the Crop tool instead (see page 89). You can also use the Crop command to reduce the image size.

To change the canvas size:

1.
If the image contains a Background (you can look for it on the Layers palette), choose a Background color (see pages 179–182) .


The original image


2.
Choose Image > Canvas Size .



3.
Optional: Choose a different unit of measure from the pop-up menus. If you choose “columns,” the current Column Size: Width setting in Edit (Photoshop, in OS X) > Preferences > Units & Rulers will be used as the increment.

4.
Enter new Width and/or Height values. Changing one dimension has no effect on the other dimension.

or

Check Relative, then enter the amount by which you want to increase each dimension. Enter a negative value to decrease a dimension.

5.
Optional: To reposition the image on its new canvas, click an unoccupied Anchor square (a square that has an arrow). The dark gray square represents the existing image area.

6.
Click OK. Any added areas will automatically be filled with the current Background color (unless the background is a layer with transparency, in which case the added canvas areas will be transparent) .


The same image with added canvas pixels


A whole image can be cropped using the Crop tool, the Crop command, or the Trim command. First, the Crop tool.

To crop an image using a marquee:

1.
Choose the Crop tool (C).

2.
Drag a marquee over the portion of the image that you want to keep .


Marquee the portion of the image you want to keep.


3.
Do any of the following on the Crop tool options bar:

Check Shield if you want the area outside the crop marquee to be darkened by a cropping shield (it helps you see what will be left) . Click the Color swatch if you want to change the color for the darkened area, and choose an Opacity for the shield color.


The Crop tool options bar after drawing a marquee with the tool


If you’re cropping a layer, click Cropped Area: Delete to have Photoshop delete the cropped-out areas. Or click Hide to have them save with the file and extend beyond the edge of the current image area. Use the Move tool to reposition any hidden layer pixels that extend off the edge. This option is available for a layer, but not for the Background.

For the Perspective option, see online Help.

4.
Do any of these optional steps:

To resize the marquee, drag any handle (double-arrow pointer). Shift-drag to preserve the marquee’s proportions. Alt-drag/Option-drag to resize the marquee from its center.

To reposition the marquee, position the pointer inside the marquee, then drag.

To rotate the marquee, position the cursor outside it (curved arrow pointer), then drag in a circular direction. To change the axis point around which the marquee rotates, drag the circle away from the center of the marquee before rotating. (The crop marquee can’t be rotated for an image in Bitmap mode.)

5.
Press Enter/Return .


The cropped image


or

Double-click inside the marquee.

or

Click the on the options bar.

If you rotated the marquee, the rotated image will be squared off in the image window.

Tip

To cancel the cropping process before accepting it, press Esc, or click the on the options bar.


Tip

To resharpen an image after cropping, apply the Unsharp Mask filter (see pages 84–85).


To specify dimensions and resolution as you crop an image:

1.
Choose the Crop tool (C).

2.
On the Crop options bar, enter Width and/or Height values .


The options bar before drawing a marquee with the Crop tool


or

Click Front Image to insert the current image’s Width, Height, and Resolution values into those fields. Use this option if you want to crop one open image to the dimensions of another open image.

The crop marquee will match this width-to-height ratio.

3.
Optional: Modify the Resolution. If, after clicking Front Image, you raise the current resolution and then crop, the print size will decrease. If you lower the current resolution and then crop, the print size will increase. In both cases, the pixel count will remain unchanged.

(To empty the Width, Height, and Resolution fields, click Clear.)

4.
Drag a crop marquee on the image, then double-click inside the marquee, or press Enter/Return, or click the on the options bar.

Unsnap

Normally, when resizing a crop marquee, if View > Snap To > Document Bounds is on, the crop edges will snap to the edge of the image. To override this snap function (let’s say you want to crop slightly inside the edge of the image), turn the Snap To > Document Bounds feature off, or start dragging a marquee handle, then hold down Ctrl-Shift-/Cmd-Shift as you drag the handle near the edge of the image.


Cropping with a marquee that’s larger than the image effectively increases the image’s canvas size.

To enlarge an image’s canvas area using the Crop tool:

1.
Enlarge the image window so the work canvas (gray area) around the image is showing.

2.
Choose the Crop tool (C).

3.
Draw a crop marquee within the image.

4.
Drag any of the handles of the marquee into the work canvas . If areas of the image originally extended outside the canvas border, those areas can now be included.




The newly cropped image has different proportions. In our example, the added pixels filled automatically with black, our current Background color, because the default Background wasn’t changed (Layers palette).


5.
Double-click inside the marquee, or press Enter/Return, or click the on the options bar. If there were no hidden pixels, and if the bottommost layer is the Background, the added canvas area will fill with the current Background color. If the bottommost layer is a layer, the added canvas area will fill with transparency.

Crop an image to fit inside another

Open both images, activate the destination image, choose the Crop tool (C), click Front Image on the Crop options bar, activate the image you want to crop, then draw a marquee. After cropping, Shift-drag-and-drop the layer from the Layers palette or copy and paste the layer onto the destination image. The resolution will adjust automatically.


The Crop command is simple and straightforward, but it’s only useful if you don’t need any of the options that the Crop tool provides. You start by drawing a selection marquee.

To crop an image using the Crop command:

1.
Choose the Rectangular Marquee tool (M or Shift-M).

2.
Draw a marquee over the part of the image you want to keep.

or

To control the size of the marquee, use the Style: Fixed Aspect Ratio or Fixed Size options on the Rectangular Marquee tool options bar, then click on the image.

3.
Choose Image > Crop, then deselect (Ctrl-D/Cmd-D).

To quickly trim away excess transparent or color areas from around an image, use the Trim command.

To crop an image using the Trim command:

1.
Choose Image > Trim.

2.
Click a Based On option :


The Trim command removes excess transparent areas or color areas, depending on which Based On option you click.


Transparent Pixels trims away any extra transparency at the edges of the image, while preserving all image pixels.

Top Left Pixel Color removes any border areas that match the color of the uppermost-left pixel in the image.

Bottom Right Pixel Color removes any border areas that match the color of the lowermost-right pixel in the image.

3.
Check which areas of the image you want the command to Trim Away: Top, Bottom, Left, or Right.

4.
Click OK.

Note: The Rotate Canvas > Flip Canvas Horizontal and Flip Canvas Vertical commands, discussed below, flip all the layers in an image. If you want to flip just one layer at a time, use Edit > Transform > Flip Horizontal or Flip Vertical instead.

To flip an image:

To flip the image left to right, choose Image > Rotate Canvas > Flip Canvas Horizontal .


The original image



The image flipped horizontally


or

To flip the image upside-down to produce a mirror image, choose Image > Rotate Canvas > Flip Canvas Vertical .


The original image flipped vertically


Note: The Rotate Canvas commands, discussed below, rotate all the layers in an image. To rotate one layer at a time, use a rotate command from the Edit > Transform submenu instead.

To rotate an image by a preset amount:

Choose Image > Rotate Canvas > 180°, 90° CW (clockwise), or 90° CCW (counterclockwise).

To rotate an image by specifying a number:

1.
Choose Image > Rotate Canvas > Arbitrary.

2.
Enter an Angle between -359.99° and 359.99° .


You can enter a custom Angle in the Rotate Canvas dialog box.


Tip

To straighten out a crooked scan, measure the angle using the Measure tool, then enter that angle.

3.
Click °CW (clockwise) or °CCW (counterclockwise).

4.
Click OK .


The original image



The image rotated 180°. Compare with the flipped images on the previous page.


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