Trước khi áp dụng điều chỉnh hoặc imageediting lệnh, bạn cần chắc chắn rằng tài liệu của bạn có kích thước thích hợp và định hướng và là cắt theo ý thích của bạn. Trong chương này, bạn sẽ tìm hiểu làm thế nào để thay đổi độ phân giải, kích thước của một tài liệu, và kích thước vải, và làm thế nào để cắt, lật, xoay, và ép nó. | Before applying adjustment or image- editing commands you need to make sure your document has the proper size and orientation and is cropped to your liking. In this chapter you will learn how to change a document s resolution dimensions and canvas size and how to crop flip rotate and straighten it. Changing the document resolution and dimensions In this section you ll encounter three related terms A file s pixel count or pixel dimensions is arrived at by multiplying its pixel height and width as in 3000 x 2000 pixels . The resolution or res for short is the fineness of detail in a document and is measured in pixels per inch as in 250 or 300 ppi . The process of changing a file s pixel count adding or deleting pixels is known as resampling. Some input devices . digital cameras that capture 8 megapixels of data or more and high-end scanners produce files with a higher pixel count than is needed for most standard printing devices. In Photoshop you can take advantage of a file s high pixel count to increase its print size or print resolution. You can keep the pixel count constant as you increase the print size and thereby lower the resolution or increase the resolution and thereby lower the print size . No resampling occurs in either case so the image quality isn t diminished. You will need to resample a file if it contains too few or too many pixels to meet the resolution requirement of your target output device. If you resample a file as you increase its resolution pixels will be added to it and its storage size will increase accordingly. Resample a file as you decrease its resolution downsample it and pixels will be deleted. The only way to get those pixels back is by clicking a prior state on the History panel before closing the file. Even more important resampling reduces the image clarity. This can be a problem for print output depending on the output resolution and how drastically the file is resampled although it can be remedied somewhat by applying a .
