Photoshop Elements 15 For Dummies - Obermeier Barbara

Скачать книгу

saved as a different file. The bitmap was converted to grayscale and dropped on top of the RGB image. After you adjust the opacity, the result is a grainy effect with desaturated color.

image

       FIGURE 2-5: You can create some interesting effects by combining the same image from a bitmap file and an RGB file.

      You can acquire Bitmap mode images directly in Elements when you scan images that are black and white. Illustrated art, logos, or your signature might be the kinds of files you scan directly in Bitmap mode. Additionally, you can convert your images to Bitmap mode.

      Converting RGB color to bitmap is a two-step process. You need to first convert to grayscale and then convert from grayscale to bitmap. If you select the Bitmap menu command while in RGB color, Elements prompts you to convert to grayscale first.

       technicalstuff The Elements Bitmap mode isn’t the same as the Windows .bmp file format. In Elements, Bitmap mode is a color mode. A Windows .bmp file can be an RGB color mode image, a Grayscale color mode image, or a Bitmap color mode image.

      To convert from RGB mode to Bitmap mode, do the following:

      1. In the Photo Editor workspace, open an image that you want to convert to Bitmap mode in either Expert or Quick mode.

      2. Choose Image ⇒ Mode ⇒ Bitmap.

      If you start in RGB mode (which is generally the case), Elements prompts you to convert to grayscale.

      3. At the prompt click OK.

      The Bitmap dialog box opens and provides options for selecting the output resolution and a conversion method.

      4. Select a resolution.

By default, the Bitmap dialog box, as shown in Figure 2-6, displays the current resolution. You can edit the Output box and resample the image or accept the default. See the section “The Art of Resampling,” earlier in this chapter, for more on changing image resolutions.

      5. From the Use drop-down list, choose a method for converting an RGB image to a bitmap image.

      Your options are as follows:

      ● 50 % Threshold

      ● Pattern Dither

      ● Diffusion Dither

Figure 2-7 shows the effect each method creates.

      6. Click OK to convert your image to Bitmap mode.

image

       FIGURE 2-6: Type a resolution for your output and choose the conversion method from the Use drop-down list.

image

       FIGURE 2-7: An original RGB image converted to bitmap by using 50 % Threshold, Pattern Dither, and Diffusion Dither.

       Converting to Grayscale mode

      Grayscale images have black-and-white pixels and any one of an additional 254 levels of gray. By converting an RGB image to grayscale, you can make a color image look like a black-and-white photo.

       warning You can convert an image to grayscale in one of three ways, but remember that one of these methods isn’t as good as the others. We recommend that you avoid converting to grayscale by choosing Image ⇒ Mode ⇒ Grayscale. When Elements performs this conversion, it removes all the color from the pixels, so you lose some precious data during the conversion and can’t regain the color after conversion. If you were to convert an image to grayscale, save the file, and delete the original from your hard drive or memory card, the color image would be lost forever. You could save a secondary file, but this method can add a little confusion and require some more space on your hard drive.

      The following two sections explain better ways to create a grayscale image.

       Desaturating a layer

      You don’t have to give up your color data when you convert to grayscale. As an alternative to using the menu command for converting images to grayscale, follow these steps:

      1. Open an RGB image in Elements in Expert mode.

      2. Duplicate a layer.

      The default Panel Bin contains the Layers panel. In this panel, click the icon in the upper-right corner. From the pop-up menu, choose Duplicate Layer. (A layer is like a clear sheet of acetate that you can draw on, only its digital. For information on working with layers, see Chapter 8.) In this example, we duplicated the layer, adjusted the duplicate layer, and duplicated again to create a third layer.

       tip You can also duplicate a layer by dragging the layer name to the New Layer icon at the top of the Layers panel.

3. Choose Enhance ⇒ Adjust Color ⇒ Adjust Hue/Saturation to open the Hue/Saturation dialog box, as shown in Figure 2-8.

      Alternatively, you can press Ctrl+U (⌘ +U on the Mac).

      4. Drag the Saturation slider to the far left to desaturate the image on the selected layer and then click OK.

      All color disappears, but the brightness values of all the pixels remain unaffected. (For more information on using the Hue/Saturation dialog box and the other Adjust Color commands, see Chapter 10.)

      5. Turn off the color layer by clicking the eye icon in the Layers panel.

In the Layers panel, you see three layers, as shown in Figure 2-9. The top layer in RGB color is hidden from view (notice the diagonal line through the eye icon). The second layer is grayscale. You don’t need to turn off the color layer to print the file in grayscale, but turning it off can help you remember which layer you used the last time you printed or exported the file.

image

       FIGURE 2-8: Open the Hue/Saturation dialog box and move the Saturation slider to the far left to eliminate color.

image

       FIGURE 2-9: The Layers panel shows the grayscale and color layers. You can turn layers on or off by clicking the eye icon.

      Following the preceding steps provides you with a file that contains both RGB and grayscale information. If you want to print the color layer, you can turn off the grayscale layer. If you need to exchange files with graphic designers, you can send the layered file, and then the design professional can use both the color image and the grayscale image.

      The other advantage of converting RGB color to grayscale by using the Hue/Saturation dialog box is that you don’t disturb any changes in the brightness values of the pixels. Moving the Saturation slider to desaturate the image affects only the color. The luminance (lightness or darkness of any given color) and hue (color) values remain the same.

       Choosing the Convert to Black and White command

A menu command exists for converting color images to black and white. Choose Enhance ⇒ Convert to Black and White in either Expert or Quick mode to get to the Convert to Black and White dialog box, as shown in Figure 2-10.

Скачать книгу