DPI of digital image: DPI means 每英寸点数. This number is calcul ated using your digital images pixel dimensions and digital image size.
The DPI (dots per inch) of an image is simply metadata embedded inside the image header. The actual dimensions i.e. the resolution of the image dows not changes when its DPI value is changed. Digital images are made up of square -shaped dots (pixels). And, the mor e dots a digital image has, the clearer the image, which is why you want to use high resolution (lots of dots) images to make Photographic Prints and Fine Art Prints.
There are three different ways to describe a digital images resolution that essentially mean the same thing:
(1) Total pixel dimensions
(2) DPI at a certain digital image size
(3) DPI at a certain output size.
The total pixel dimensions of an image will tell you how many total pixels (dots) the image is made up of. For example, lets say we have a digital image that is 1200x1800 píxeles (dots). That means our digital image is 1200 dots high by 1800 dots wide. So, unless you resample (which means you artificially alter the pixel dimensions in a photo editing program) or crop the image, your image will always be 1200x1800 píxeles.
People regularly discuss digital images in terms of DPI, which stands for 每英寸点数. The DPI of a digital image is calculated by dividing the total number of dots wide by the total number of inches wide OR by calculating the total number of dots high by the total number of inches high.
Lets say we have a digital image that is 12 00x1800 píxeles (dots) and 4x6 inches in size. That means our digital image is 1200 dots high by 1800 dots wide and 4 inches high by 6 inches wide. Our digital image has 300 DPI. I figured that out by dividing the number of dotswide by the number of inc hes wide:
1800 dots wide / 6 inches wide = 300 dots / 1 inch = 300 每英寸点数