Iam not an expert , Cái này kiếm ngoài Net thử xem work không.
Cropping methods You can crop an image using the crop tool, the Crop command, or the Trim command. Use the crop tool when you need more options for cropping an image. You can rotate or scale the selected area before cropping. If you're working with more than one image file, you can apply specific cropping dimensions for all the crops. In Photoshop, you can also specify image resolution for the crop. Selecting Perspective in the options bar transforms and crops images of rectangular objects like architecture. (See Transforming perspective (Photoshop) <Program%20FilesAdobePhotoshop%206.0Helpc07tr4.htm>.) To crop an image using the crop tool: 1 Select the crop tool ( ). 2 Do one of the following: · (Photoshop) If you want to specify the size and resolution of the crop, enter the values in the options bar, or click Front Image to enter the values of the current image. · (ImageReady) Select Fixed Size in the options bar, then enter image dimensions for the crop, or click Front Image to enter the values of the current image. 3 Drag over the part of the image you want to keep. When you release the mouse button, the crop marquee appears as a bounding box with handles at the corners and sides, and a cropping shield covers the cropped area. 4 In the options bar, select Delete or Hide. 5 Select the Shield option to show or hide the cropping shield. To adjust the color and opacity of the cropping shield, use the color selection box and the opacity pop-up slider in the options bar. 6 (Photoshop) If you are transforming and cropping an oblique rectangular image, select Perspective. (See Transforming perspective (Photoshop) <Program%20FilesAdobePhotoshop%206.0Helpc07tr4.htm>.) 7 Adjust the crop marquee: · To move the marquee to another position, place the pointer inside the bounding box, and drag. · To scale the marquee, drag a handle. To constrain the proportions, hold down Shift as you drag a corner handle. · To rotate the marquee, position the pointer outside the bounding box (the pointer turns into a curved arrow), and drag. To move the centerpoint which the marquee rotates around, drag the circle at the center of the bounding box. Note: In Photoshop, you can't rotate the crop tool marquee for an image in Bitmap mode. 8 To crop the image, press Enter (Windows) or Return (Mac OS). You can also click the OK button ( ) in the options bar to crop the image. 9 To cancel the cropping operation, press Esc. In Photoshop, you can also click the Cancel button ( ) in the options bar to cancel the cropping operation. To crop an image using the Crop command: 1 Select the part of the image you want to keep. For more information about setting marquee options, see Using the marquee tools <Program%20FilesAdobePhotoshop%206.0Helpc06se5.htm>. 2 Choose Image > Crop. To crop an image using the Trim command: 1 Choose Image > Trim. 2 In the Trim dialog box, select an option: · Transparent Pixels to trim away transparency at the edges of the image, leaving the smallest image containing non-transparent pixels. · Top Left Pixel Color to remove an area the color of the upper left pixel from the image. · Bottom Right Pixel Color to remove an area the color of the lower right pixel from the image. 3 Select one or more areas of the image to trim away: Top, Bottom, Left, or Right. 4 Click OK.