Tham khảo tài liệu 'hướng dẫn sử dụng coreldraw x5 - part 73', công nghệ thông tin, đồ họa - thiết kế - flash phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 704 CorelDRAW X5 The Official Guide size check for visible artifacts in your print and if there s visible corruption go back to your original or seriously consider reshooting the image. One of the methods CorelDRAW PHOTO-PAINT and other programs that can import bitmaps use to lessen and occasionally eliminate visible artifacting from resampling a photo is called anti-aliasing and you have some control over this method discussed later in this chapter. Anti-aliasing is a math calculation that performs averaging in a resulting photo that s been altered in areas where there is visual ambiguity some of the pesky pixels are traveling under an alias . For example suppose you could photograph a checkerboard plane that extends from your feet way out to the horizon. You look down toward your feet and clearly see black squares and white squares. You look at the horizon and you do not see clear edges of the black and white squares actually you ll see a lot of gray as your mind blends black and white together because your eyes don t have photoreceptors fine enough to resolve the very distant black and white squares. Similarly our computers cannot reconcile black and white areas in a digital image that are smaller than the size of the pixels in the image so when you resample the image they create inaccurately little black and white squares where they shouldn t be. The inaccuracy means the black and white squares are traveling as an alias and presenting themselves falsely. Anti-aliasing comes to the designer s rescue by averaging pixel colors when you resample such a checkerboard photo or any photo. The anti-aliasing technique examines in this example areas that include both a white square and a black one understands that both colors can t be assigned to only one pixel and so writes a blend of colors gray to the new pixel color value. At left in this illustration you can see some unwanted patterning toward the horizon this image was not anti-aliased when it was resampled to .
