Changing Resolution

Change the resolution of paint objects in two ways:

• If you do not want to change an object’s size, resample the image. Resampling merges or divides pixels.
• If you want to preserve all the data in an image, change the object’s resolution and allow its size to change.

Decreasing resolution (“down sampling”) decreases file size by discarding data, which can result in lost detail; however, it’s common to reduce resolution in some situations.

For Web pages and other applications where images are displayed on a monitor, 72 ppi is the standard resolution.

Rarely, an image is resampled to increase resolution. This should be avoided because additional pixels are created by estimating their color values, which does not improve an image.

The Resolution dialog box has compact and expanded states. In its compact state, you can easily change the resolution of multiple paint objects without needing to specify additional options. (See Image Resolution Settings.)

Image Resolution Settings

Specify the resolution, width, and height for a selected paint object when the Image Resolution dialog box is expanded. Expand the dialog box when a single paint object is selected; if multiple objects are selected, they must match in size and resolution.

Depending on the options you select, certain settings in the dialog box can’t be changed. A bracket and chain icon indicate settings that are linked and fixed.

• Preserve Data: Prevents resampling, or interpolation, when resolution or size changes. Selecting Preserve Data also selects Preserve Proportions, so width and height change only in proportion to each other.

Preserve Data means image resolution and size are relative; changing the resolution will change the object size, and changing the size will change the image resolution.

If you select Pixels in the Width and Height menus, you cannot change these values, because the number of pixels cannot change when Preserve Data is selected.

• Width and Height: Specify a size for the paint object by entering values in these text boxes. Select measurement units in the adjacent menus.

The width and height boxes show the size a paint object will become if you change the resolution when Preserve Data is selected.

• Preserve Proportions: This option links the Width and Height values so that changing one value changes the other and maintains the original proportions of the paint object. Selecting Preserve Data also selects this option. If you want to stretch a paint object in only one direction, deselect Preserve Proportions.

When more than one paint object is selected (unless the objects are the same size and resolution), the button that displays additional options in the Resolution dialog box is not available.

To Change Resolution by Resampling:

This procedure reduces resolution of paint objects for use on a Web page or in a presentation.

1. Select one or more paint objects. These objects can vary in size and resolution.
2. Choose Image | Area | Resolution. The Image Resolution dialog box appears in its compact state.
3. Select pixels per inch or pixels per centimeter and enter the resolution value in the text box.
4. Click OK. Canvas X Draw changes the resolution of the selected objects, which remain the same size.

To Change Resolution without Resampling:

Use this procedure to change the resolution of paint objects without resampling. This changes the size of objects while preserving the image data.

If you reduce resolution, paint objects become larger because the individual pixels are larger. If you increase resolution, paint objects become smaller because the individual pixels are smaller.

1. Select one or more paint objects and choose Image | Area | Resolution.
2. In the Image Resolution dialog box, select Preserve Data.
3. Enter the desired resolution in the text box and click OK. Canvas X Draw changes the resolution of the selected paint objects.

To Calculate Resolution:

If only one object is selected, you can calculate an appropriate resolution based on a halftone screen frequency.

1. Click Auto in the Image Resolution dialog box.
2. Enter the screen frequency and choose Draft, Good, or Best. Canvas X Draw calculates the resolution by multiplying the screen frequency by 1 (draft), 1.5 (good), or 2 (best).
3. Click OK to enter the calculated resolution in the Image Resolution dialog box.

Resampling and Sharpening Images

Resizing and resampling causes images to appear softer. However, you can apply the Unsharp Mask filter to bring soft images back into focus. For more information, see To Apply the Unsharp Mask Filter.

Original 300 ppi	Resampled down to 150 ppi
150 ppi image resampled up to 300 ppi	150 ppi image with Unsharp Mask filter applied Amount = 80 Radius = 1.6 Threshold = 0
300 ppi image with Unsharp Mask filter applied Amount = 67 Radius = 1.6 Threshold = 0

To Specify How Canvas X Draw Approximates New Pixels:

When increasing image resolution, Canvas X Draw uses one of two methods to calculate color values for the pixels it adds to an image. To change the method, use the Interpolation control in the Preferences dialog box.

1. Choose Canvas X Draw | Preferences. Select the Painting manager in the General settings.
2. Select an option under Interpolation and click OK. For more information, see Setting Preferences.

See Also:

• Sharpen Filters