Print image resolution calculation
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1. Digital images processed by computers are also called dot matrix graphics. You can think of dot matrix graphics as a combination of square patches of many different colors, and each square of different colors we have. It is called a pixel (Pixel).
2. Resolution refers to the number of dots or the number of pixels in a unit of digital image. For example, an image resolution of 100 dots per inch is called 1OODPI (Dots Per Inch).
3. In some digital image processing software, each point is called a pixel (Pixel), so the unit of resolution is also called PPI (Pixels Per Inch), whether it is DPI or PPI (DPI, this is a The more common unit), from the impression of the traditional traditional print photos, we can know that the finer the particles of the film and the photo paper, the finer the image quality of the photo will be.
Since digital images are composed of pixels, naturally the higher the resolution (that is, the number of pixels contained in the unit length), the better the quality of the digital image. Therefore, it is conceivable that the image quality of the 300DPI digital image will definitely be better than the 72DPI digital image.
4. Before scanning an image into a digitized electronic image file, the output resolution and image magnification of the printed product must be determined.
5. Magnification is the ratio of the print size of the image to the original size.
6. The resolution of printed matter is usually in units of Line Per Inch per unit length, depending on the type of printed matter and the type of paper. Generally speaking: newspaper: 85lpi; color magazine: 133, 150 or 175lpi; art album: 200lpi
7. Generally, when we use paper with smooth surface such as snow-copper paper as the printing material, we will choose 300pixels/inch (DPI) or 118pixels/cm (DPC) resolution for digital image printing. The resolution is used to achieve 150 line (150 Lines Per Inch) quality when printing.
8. The resolution of the digital image used on various types of printed matter depends on the value of the printed network cable to which the printed material is applied. If you want a higher quality of the network cable, the resolution of the digital image needs to be increased. Generally, the network cable value can be multiplied by twice, which is the resolution value that the digital image should have. If the image needs to be enlarged, you must multiply the magnification as shown in the following formula:
Scanned image resolution = number of printed network lines x 2 x magnification
For example, the number of printed network lines is 150 lines, and the image size must be magnified by 3 times. The scanning resolution must be 9OODPI (150 LPIx 2x3 times). Another example: When the printing network line is 175lpi, if you want to print the image in the original size, it is best to scan the image with a resolution of 35Oppi. If you want to magnify the image by two times, you should use a scan resolution of 70Oppi.
9. When processing Line Art, the resolution of the output device should be used as the scanning resolution. For example, to output 12OOdpi black and white photographic paper, you should use 12OOppi as the scanning resolution. If only 300dpi electric printer is used for output, then 30Oppi can be used as the scanning resolution.