How does indesign judge whether a picture is accurate enough to print?

In the picture, press F8 to view the picture information. If it is 300ppi, it is the printing standard. If it is less than 300, the quality of the printed picture will decrease.

Requirements for pictures when printing: Not all pictures can be printed. Download a picture casually from the Internet, it looks good on the screen, but it may be rough and color cast when printed, because the resolution of the screen is low and the defects of the picture are not easy to detect on the screen.

The basic requirements for printing pictures are embodied in four aspects: file format, color mode, bit depth and resolution. Further requirements are color, layering and image quality. Some are quantitative, some are qualitative, some are soft indicators, which can be improved if they fail to meet the requirements, and some are hopeless.

Basic requirements: file format, color mode, bit depth and resolution.

Please use Photoshop to open various image files on your computer and view the following items:

1. file format: you can see the file name in the title bar of the document window, and its suffix is the file format.

1. file format, no matter how many formats the manuscript has and when it is released:

There are only three options: tif, eps, pdf and tiff are the most commonly used. Scans of various manuscripts, pictures copied from the library and pictures on the Internet can all be saved in tif format. The output folder of a design company is often a typesetting file, which contains many tif drawings. You can have eps or pdf, but you can't have jpg, glf, png, etc. Their influence is unpredictable.

There are special reasons for using eps or pdf.

The first reason is: to make a vector diagram. Appendix 2 has a detailed explanation of the vector diagram. Now, to put it simply, a vector diagram is a diagram that can arbitrarily improve the resolution when printing. A logo drawn in Core|Draw will appear on the film when the printing resolution is 24∞dpi, and it will be clearer when the printing resolution is higher. On the contrary, it is a bitmap. The logo scanned from the book is a bitmap. If its resolution is 3 pi, it will always be 3∞dpi when printing, without details. Tif is the format of bitmap, and eps or pdf is the format of vector diagram. You can choose the saved or exported format in typesetting software and image processing software.

The second reason: I want to merge the vector map and bitmap into one file.

After doing this experiment, you will immediately understand what vectors and bitmaps look like: open a photo image in Photoshop, enter some words without rasterization or layering, then save it in pdf format, open it with AcrobatReader, and enlarge it again. You will find that the bitmap is blurred and the words are clear. This file contains bitmaps and vector diagrams. The base map is a bitmap, which becomes blurred after enlargement, and the text is a vector map, which remains clear no matter how many times it is enlarged. If you take this pdf out, you can improve the resolution of the text at will, but not the base map. The same is true for saving in eps format.

Pure bitmap can also be saved in eps or pdf format, but it is not necessary. Saving a photo with eps or pdf will increase the time of saving and opening in vain. Eps or pdf can only keep the vector nature of vector images, and can't turn bitmaps into vector images. Just save the photo as tif.

Second, color mode: you can see the color mode in the title bar of the crotch window or in "Picture >"; Mode menu to see which color mode:

Color mode is a way to describe colors by dividing them into specific components. RGB mode describes the contents of three primary colors, namely red, green and blue, while CMYK mode describes the proportion of four inks, namely cyan, magenta, yellow and black. No matter what mode the manuscript is in, it should be converted into one of the following modes before publication: CMYK, grayscale, black and white binary. The way to turn is in Photoshop "Image >"; Mode "menu under the corresponding entry. Which mode to switch to depends on the printing ink.

Four-color printing, using CMYK mode. For monochrome printing, gray mode is adopted. Monochrome printing is a special case, that is, just like mechanical structure drawing, lines and color blocks need to be printed with 100% ink without screening. This kind of drawing can adopt black-and-white binary mode (Photoshop Chinese version calls it bitmap mode, but the bitmap here is different from the bitmap just mentioned).

Third, bit depth: in "Image"; Mode "menu view, is a few/channel.

There can be 2n colors in a color space, which is called n-bit. The black-and-white binary mode is 1 bit, because there are only 2 1 colors-pure black and pure white. There are three options for other color modes: 8-bit/channel, 16-bit channel and 32-bit/channel, which should be changed to 5-bit/channel before making movies.

Fourth, resolution: in "Image"; Image Size menu opens the dialog box to see how many pixels/inch it is.

We can see that the image file formats are jpg, tif, eps, bmp, gif, pr 19, tga and so on. The color modes are RGB, index color, CMYK, gray, black and white, etc. The resolution can be 72dpi, 230dpi, 30Odpi, etc. So what can be used for printing?

The resolution of prepress image should be at least 30Odpi. However, if the logo pattern and text must be made into a bitmap, it is best to reach more than 360 ODPI to ensure clear output. If the color module is black and white, the resolution should be higher. In Section 4.5, the main mechanical structure drawings are scanned with the resolution of 12∞dpi.

When the resolution can't meet the requirements, you can use Photoshop's "main image size" command to adjust. For example, the online map is 72dpi, and the 3 here can be changed to 30Odpi. But you must cancel the reset of image pixels before changing it, so as to keep the number of pixels unchanged? It's the same picture quality. This will reduce the print size. If there are too many, you can check M to reset the image pixels and change the print size. Don't make it too big, or it will become blurred. For doctors with 72dpi, if the print size is not reduced, lj30Odpi will become blurred.