Printing prepress staff can not be ignored three knowledge

I. bitmap images and vector graphics

Computer graphics into bitmap images and vector graphics into two categories, recognize their characteristics and differences, help create, input, output, and digital image editing. Bitmap images and vector graphics no good or bad, just different purposes only. Therefore, the integration of bitmap images and vector graphics advantage, is the best way to deal with digital images.

1. bitmap image

Bitmap images, also called raster images, Photoshop and other graphics software generally use a bitmap image. Bitmap image composed of pixels, each pixel is assigned a specific location and color value. When working with bitmap images, you edit pixels rather than objects or shapes, that is to say, edited every point.

2. Vector Graphics

Vector graphics line defined by the vector and curves, AdobeIllustrator, CorelDraw, CAD and other vector graphics software is the basis of creation. Vector graphics will be described according to the geometric characteristics of the profile. After the contour pattern shown, it is placed in a particular position and fill color. Move, resize or change the color does not degrade the quality of the graphic.

II. Resolution

Resolution is a measure of the performance capabilities of image detail, in the image processing, the concept is often related to the resolution There are several different forms:

1. Image resolution

Image resolution is the number of pixel-image linear dimensions included, usually in pixels / inch (ppi) as the unit of measurement is the same as the print size of the two images, high resolution images than the low-resolution images included more pixels, for example: print size is 11 square inches of image, if the resolution is 72ppi, the number of pixels that is contained in 5184 (7272 = 5184) If the resolution is 300ppi, the number of pixels contained in the image resolution compared to 90000.. Rate images using more pixels, the print that they can reproduce more detailed and finer color shift than low resolution images in the unit area.

2. Display Resolution

Display resolution refers to the number displayed on the display unit length per pixel, or dot, usually in dots inch (dpi) for the unit of measurement. Monitor resolution depends on the display size and pixel setting, PC monitor typical resolution of 96dpi.

III. Color Mode

When performing image processing, color mode to establish a good description and reproduce color model, each model has its own characteristics and scope, the user can be determined according to the production requirements of the color mode, and can be based required between the different color modes. Next, we introduce the concept of some commonly used color modes.

1.RGB color mode

Nature, most of the visible spectrum can be used red, green and blue light by mixing different proportions and intensity to represent. RGB representing the three colors: R for red, for green G, B for blue. RGB model is also called additive color model, as shown in Fig. RGB model is usually used for lighting, video and image editing screen.

2.CMYK color mode

CMYK color mode for printing ink on the paper-based light absorption characteristics, image, each pixel is made indigo (C), magenta (M), yellow (Y) and black (K) color composite in accordance with different proportions  Each printing ink of each pixel is assigned a percentage value, the lower the brightest (highlight) color printing ink color assigned a percentage value, the higher the darker (shadow) colors assigned a percentage value. For example, bright red might contain 2% cyan, 93% magenta, 90% yellow and 0% black. In CMYK images, when the values of all four kinds of components are 0%, it will have pure white. Image CMYK color mode contains four channels, as shown in Figure 6. We have seen this pattern is composed of four-channel synthesis effect.

When preparing an image for printing color printing, CMYK color mode to use. RGB image is converted to CMYK color mode color mode produces images separations. If you use the image material for RGB color mode, it is best done in editing and then convert to CMYK color mode.

3.HSB color mode

HSB color model is based on the human visual feature of everyday life and the development of a set of eye color mode, the color closest to the human recognizable way of thinking. HSB color mode to Hue (H), saturation (S) and brightness (B) describe the basic characteristics of color.

4.Lab color mode

Lab Color mode by the luminosity component (L) and two chrominance components composed of two components namely a component (from green to red) and the b component (from blue to yellow). Lab Color mode and device-independent, no matter what device (such as a monitor, printer, or scanner) to create or output image, color This color mode produces are consistent.