Creating an image in incorrect colors can be a problem. Consider the main differences between the two RGB and CMYK color models.

RGB:

RGB consists of digits of red, green and blue. This scheme is more known as an additive model. When the light from the screen is projected onto the colors, it mixes them together on the retina, creating the necessary shades.

Additive model

Additive colors are created using a method that combines many different shades. Red, green and blue are the main colors that are used in the additive model. Combinations of two of these colors create an additional color: blue, purple or yellow.

Images in the RGB often see on the screens of televisions and computer monitors. This mode can only be used by the devices generating light. An image made in RGB is suitable for printing only on a digital printer.

If you want the layout to be printed professionally, you will have to change the color mode on CMYK.

CMYK:

CMYK deciphered Like blue, purple, yellow and black. This is a subtractive model opposite to RGB. In it, the colors are subtracted from natural white light into pigments, which are then printed on paper with tiny dots. For example, subtraction of purple color from yellow will give red.

Side colive color model

The subtractive colors begin with white. Therefore, the more colors are added, the darker they will be. The reason for this is that the light is absorbed or deleted to create different colors.

Main color for color model CMYK. - Black (K). Adding this color helps to neutralize images and increase the density of the shade.

CMYK ink will not always have the same color as the original image. But there are many CMYK combinations, when using which the image on paper looks like on a computer in RGB mode.

Programs such as Photoshop, Illustrator and Indesign provide CMYK presets that help you choose the best combination of print settings.

Why are these two modes are displayed differently?

Any image is unique, so the magnitude of the white and mixing of other colors used in it in each model will be different. As a result, both RGB and CMYK are displayed in different ways.

For example, RGB offers a wider range of colors. Therefore, the file created in this model allows you to use bright, living colors. When it is converted to CMYK, many of bright shades look dull or muddy.

When printing, regardless of the model used, the colors become darker. Check in which formats the printer can print, and collect information about the conversion of files. All printers are different, so DPI will be different.

What mode should I use?

Many designers still prefer to create their projects first in RGB, and then convert them to CMYK before sending to print. This is due to the fact that RGB supports a wider range of colors.

Another advantage is that RGB allows you to work with smaller files. And also that Photoshop, Indesign and Illustrator are based on RGB and this model is supported in the Web.

But if color accuracy is important in printed products, it is better to use CMYK. Designing in this color mode will allow you to get a clearer view of the finished product.

If you use a digital printer, save the file in the RGB format. it the best way When printing photos. Fir you have a file that you want to print on an offset full-color printer, then swing the conversion to CMYK.

Converting tools

Before conversion, save backup your file. You can enlarge the layers before conversion, but it is not necessary.

Adobe Photoshop, Illustrator and Indesign are the most common programs used to create graphic projects. They are focused on working in RGB mode.

Therefore, these editors simplify conversion to CMYK and install a specific color reproduction scheme for printing. This is followed as follows:

Illustrator: File\u003e Color Mode Document\u003e CMYK or RGB.

Indesign: Window\u003e Color\u003e CMYK or RGB.

Step-by-step instructions for setting up color modes for printing in Photoshop:

Step 1 . Select Edit menu, then " Setting flower"(Color Setting).

Step 2. Select CMYK profile that is most suitable for printing.

Step 3. You can choose the option " More parameters"To establish a color scheme when converting RGB values \u200b\u200bin CMYK. The "perceptual" method is best suited for photos, because it saves a visual matching with the original image.

Step 4. Open the RGB image you want to convert.

Step 5. Make changes while the image is still in RGB mode.

RGB model describes emitted colors. It is based on three main (basic) colors: red (Red), green (Green) and blue (Blue). The RGB model can be called "native" for the display. The remaining colors are obtained by a combination of basic. The colors of this type are called additive.

It can be seen from the drawing that the combination of green and red give yellow color, a combination of green and blue - blue, and a combination of all three colors is white. From this it can be concluded that colors in RGB are subtractive.

The main colors are taken from human biology. That is, these colors are based on the physiological response of the human eye to the light. The human eye has a photoreceptor cells that react to the most green (M), yellow-green (L) and blue-violet (S) light ( maximum length Waves from 534 nm, 564 nm and 420 nm, respectively). The human brain can easily distinguish a wide range of different colors based on differences in signals obtained from three waves.

The most wide RGB color model is used in LCD or plasma displays, such as a TV or computer monitor. Each pixel on the display can be presented in the hardware interface (for example, graphic maps) as values \u200b\u200bof red, green and blue. RGB values \u200b\u200bare changed in the intensity, which are used for clarity. Cameras and scanners also work in the same order, they capture color with sensors that register various RGB intensity for each pixel.

In 16 bits mode, the pixel, also known as HighColor, has either 5 bits on color (often referred to as 555 mode) or with an additional bit for green (known as 565 mode). The green color is supplemented due to the fact that the human eye has the ability to identify more shades of green than any other color.

RGB values \u200b\u200bpresented in 24 bits mode on pixel (BPP), also known as TrueColor, is usually distinguished by three integers between 0 and 255. Each of these three numbers is the intensity of red, green and blue, respectively.

In RGB - three channels: red, blue and green, i.e. RGB - Three-channel color model. Each channel can take values \u200b\u200bfrom 0 to 255 in decimal or, closer to reality, from 0 to FF in hexadecimal number systems. This is explained by the fact that the byte, which is encoded by the channel, and indeed any byte consists of eight bits, and the bit can take 2 values \u200b\u200b0 or 1, and tight 28 \u003d 256. In RGB, for example, a red color can take 256 gradations: from purely red (FF) to black (00). Thus, it is easy to calculate that the RGB model contains only 2563 or 16777216 colors.

In RGB, three channels, and each is encoded by 8 bits. Maximum, FF (or 255) The value gives pure color. White color is obtained by combining all colors, more precisely, their limit gradations. White Code \u003d FF (Red) + FF (Green) + FF (Blue). Accordingly, the code is black \u003d 000000. The code is yellow \u003d FFFF00, purple \u003d FF00FF, blue \u003d 00FFFF.

There are also 32 and 48 bit colors display modes.

RGB is not used for printing on paper, instead there is a CMYK-color space.

CMYK is the color model used in color printing. The color model is a mathematical model for describing colors with integers. CMYK model is built on blue, purple, yellow and black colors.

| Planning lessons for the school year (on the textbook of N.D. Uginovich) | Flower palettes in RGB color rendition systems, CMYK and HSB

Lesson 12.
Flower palettes in RGB color rendition systems, CMYK and HSB

§ 2.2.3. Flower palettes in RGB color rendition systems, CMYK and HSB

2.2.3. Flower palettes in RGB color rendition systems, CMYK and HSB

White light can be decomposed using optical devices, such as prisms, or water droplets in the atmosphere (rainbow) on various colors of the spectrum: red, orange, yellow, green, blue, blue and purple (Fig. 2.4).

Fig. 2.4. White light decomposition in the spectrum

The phrase is well known, which helps to easily remember the sequence of flowers in the spectrum of visible light: « Everyone hunter wishes know , where is sitting pheasant ».

A person perceives light with the help of color receptors, so-called colums located on the retina of the eye. The greatest sensitivity of the colums falls on red, green and blue colors, which are basic for human perception. The amount of red, green and blue colors is perceived by man as white, their absence - like black, and their various combinations are like numerous shades of colors.

Flower palette in RGB color reproduction system. From the monitor screen, a person perceives the color as the amount of radiation of three basic colors: red, green and blue. Such a color reproduction system is called RGB, according to the first letters of the English names of colors ( Red, Red, Green - Green, Blue - Blue).

Colors in the palette RGB. Formed by adding basic colors, each of which may have different intensity.

Color color can be determined using formula (2.1).

With minimal intensities of all base colors, a black color is obtained, with maximum intensities - white color. With the maximum intensity of the same color and the minimum two others - red, green and blue. The overlap of green and blue forms a blue color (Cyan), the overlap of red and green colors is yellow (yellow), the overlap of red and blue - magenta (Magenta) (Table 2.4).

Table 2.4. Forming colors in the RGB color rendering system

In the RGB color reinforcement system, the colors palette is formed by adding red, green and blue.

With a color depth of 24 bits on the encoding of each of the base colors, 8 bits are highlighted. In this case, N \u003d 2 8 \u003d 256 intensity levels are possible for each of the colors. Intensity levels are defined by decimal (from minimal - 0 to maximum - 255) or binary (from 00000000 to 11111111) codes (Table 2.5).

Flower palette in CMYK color rendering system. When printing images on printers, a palette of colors is used in the system CMY. The main paints in it are Cyan - blue, Magenta - purple and yellow - yellow.

Colors in the CMY palette are formed by imposing paints of basic colors. The color of the Color palette can be determined using formula (2.2), in which the intensity of each paint is set as a percentage:

Image printed on paper. Man perceives in reflected light. If the paints are not applied on the paper, the falling white light is completely reflected and we see a white sheet of paper. If the paints are applied, they absorb certain colors of the spectrum. Colors in the CMY palette are formed by subtracting certain colors from white light.

Blue paint applied on paper absorbs red light and reflects green and blue light, and we see blue color. Purple paint applied on paper absorbs green light and reflects red and blue light, and we see magenta color. Yellow paint applied on paper absorbs blue light and reflects red and green light, and we see yellow.

Mixing two paints of the CMY system, we get the base color in the RGB color reproduction system. If we apply purple and yellow paint on paper, then green and blue light will be absorbed, and we will see a red color. If you apply a blue and yellow paint on paper, then red and blue light will be absorbed, and we will see the green color. If we apply purple and blue paints on paper, then green and red light will be absorbed, and we will see the blue color (Table 2.6).

Mixing three paints - blue, yellow and purple - It should lead to the full absorption of light, and we must see the black color. However, in practice, instead of black color, a dirty-brown color is obtained. Therefore, another one, truly black color add in the color model. Since the letter "B" is already used to designate blue, the last letter in the English name of the black black color is adopted to designate the black color, i.e. "to". The extended palette was called CMYK (see Table 2.6).

In the CMYK color rendering system, the colors palette is formed by overlapping blue, purple, yellow and black paints.

RGB color reproduction system is used in computer monitors, televisions and other emitting lights. technical devices. CMYK color reproduction system is used in printing, as printed documents are perceived by a person in the reflected light. IN inkjet printers To obtain high-quality images, four cartridges are used, containing the basic paints of the CMYK color reproduction system (Fig. 2.5).

Fig. 2.5. Using RGB and CMYK color reproduction systems in a technique

Flower palette in HSB color rendition system. HSB color reproduction system uses as basic parameters Hue. (color shade), Saturation. (saturation) and BRIGHTNESS. (brightness).

Parameter Hue Allows you to choose the shade of color from all colors of the optical spectrum: from red to violet color (H \u003d 0 - red, H \u003d 120 - green, H \u003d 240 - blue color, H \u003d 360 - purple color).

Saturation parameter Determines the percentage of "clean" shade and white (S \u003d 0% - white color, S \u003d 100% - "clean" shade).

BRIGHTNESS Determines the color intensity (the minimum value B \u003d 0 corresponds to black color, maximum value B \u003d 100 corresponds to the maximum brightness of the selected color shade).

In the HSB color reproduction system, the colors palette is formed by setting the color, saturation and brightness values.

In the editors, it is usually possible to transition from one color reproduction model to another. This can be done both using the mouse by moving the pointer to the color field, and inserting the parameters of the color models from the keyboard to the corresponding text fields.

Control questions

1. In which natural phenomena and physical experiments can observe the decomposition of white light in the spectrum? Prepare a report.

2. How the color palette is formed in the color reproduction system RGB.? In the color reproduction system CMYK.? In the HSB color rendition system?

Tasks for self-execution

2.8. Task with a brief answer. Determine the colors if the intensities of the basic colors are specified in the color rendering system RGB.. Fill the table.

2.9. Task with a brief answer. Determine colors if paints are applied on the paper in the color reproduction system CMYK.. Fill the table.

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Signatures for slides:

White light has a complex structure.

In 1666, Isaac Newton, with the help of a glass prism, first explored the white light and installed its complex composition. Video Isaac Newton

White light has a complex structure!

Composition of white light: purple blue blue green yellow orange red to memorize colors in the spectrum enjoy a conditional phrase: "To apish about the drive, it freshers, where with the Cold of F Azan."

Human eye person perceives light using color receptors (so-called colums) located on the retina of the eye.

Basic colors The greatest sensitivity of the colums falls on red, green and blue colors, which are basic for human perception.

Lesson theme: Flower palettes in RGB, CMYK and HSB color rendition systems.

Color rendering systems: RGB (R ED, G Reen, B Lue) CMYK (C YAN, M Agenta, Y Ellow, Blac K) HSB (H UE, S Aturation, B Rightness) Red Green Blue Black Yellow Purple Blue Tint Saturation Brightness

RGB The main colors are red, green, blue. The palette of colors is formed by adding red, green and blue. The color of the palette can be determined using the formula:

Color Codes of intensity Basic Colors Red Green Blue Black 00000000 0 00000000 0 00000000 0 00000000 0 00000000 0 00000000 0 11111111 255 00000000 011111111111111111111111111111111255 yellow 111111111111111111111111111111 255 11111111 255 11111111 255 Coding of colors with color depth 24 bits

RGB is used in computer monitors, televisions and other radiating technical devices.

CMYK main colors are blue, purple and yellow. Flower palette is formed: by subtracting from white color of certain colors by overlaying blue, purple, yellow color, the color of the palette can be determined using the formula

Color Formation of color Black \u003d C + M + Y \u003d W - G - B - R white \u003d (c \u003d 0, m \u003d 0, y \u003d 0) Red \u003d y + m \u003d w - G - B Green \u003d Y + C \u003d W - R - B Blue \u003d M + C \u003d W - R - G CYAN \u003d W - R \u003d G + B Magenta \u003d W - G \u003d R + B Yellow \u003d W - B \u003d R + G Forming colors in CMYK color rendering system

CMYK is based on the perception of the non-emitted, but reflected light. It is used in printing, when printing images on printers (because printed documents are perceived by a person in the reflected light).

Most importantly: There are the following color rendering systems: RGB (R ED, G REEN, B LUE) CMYK (C YAN, M Agenta, Y Ellow, Blac K) HSB (H UE, S Aturation, B Rightness) Flower palette in RGB color rendering system Forming by adding red, green and blue. The color of the palette can be determined using the formula:

Most importantly: The main colors in the CMYK color rendition system are blue, purple, yellow. The colors palette is formed: by subtracting certain colors from white, by imposing blue, purple, yellow color. The color of the palette can be determined using the formula

Most importantly: HSB color rendering system uses HUE as basic parameters (Saturation), Saturation, BRIGHTNESS (brightness). The Hue parameter allows you to select a color shade of all colors of the optical spectrum, starting with a red color and ending with a purple parameter Saturation determines the percentage of "clean" shade and white. The BRIGHTNESS parameter determines the color intensity

Tasks: Task 1.7 (p.21) Determine colors if the intensities of the base colors are specified in the RGB color reaction system Task 1.8 (p.21) to determine colors if paints are applied in the CMYK color reproduction system.

Task 1.7 Color Intensity of primary colors Red Green Blue 00000000 00000000 11111111 00000000 00000000 00000000 00000000 11111111 00000000 00000000 00000000 11111111 00000000 11111111 11111111 11111111 00000000 11111111 11111111 11111111 00000000 11111111 11111111 11111111

Task 1.8 (p.21) Color formation (c \u003d 0, m \u003d 0, y \u003d 0) y + m \u003d w - G - by + C \u003d W - R - BM + C \u003d W - R - GW - R \u003d G + BW - G \u003d R + BW - B \u003d R + G

Color models RGB and CMY (CMYK)

RGB (for displays) and CMYK (for printing) are the most common color representation systems.

The main model of the color synthesis is the CMYK printing system (blue-green / blue, purple, yellow, key / black).

The most common variant of the additive mixing involving the summation of multi-colored streams into a single resulting stream is the RGB model (red, green, blue).

If the subtractive scheme is used in printing (with white zero - lack of paint on paper), then additive (having large color coverage) - in televisions, monitors, etc., where the screen turned off black.

Since RGB and CMY complement each other, there is a certain ratio between them. If you show this information in the form of one color circle, then the RGB and CMY colors will change in it alternately. If you mix two RGB colors, you will get a CMY-color; If, on the contrary, mix two CMY-colors, then this time it turns out the RGB-color. For example, in the CMY model, the red color is described as a mixture of purple and yellow. And in the RGB model, purple color is described as a mixture of red and blue.

In addition, in comparison with RGB, CMYK has smaller color coverage. Physics laws do not allow printing RGB colors. For the printing of the RGB image, it is necessary to convert its additive colors to CMY colors, i.e. Translate them to subtractive colors.

RGB color rendering system

RGB (eng. Red, Green, Blue - Red, green, blue) - additive color model (eng. AdDitive PRIMARY MODEL) , Describing the color synthesis for color reproduction. The additive model is called because colors are obtained by adding (eng. aDDITION ) To black color. The choice of primary colors in RGB is due to the peculiarities of the physiology of perception of the color of the retina of the human eye.

The RGB model is used to play the spectrum of visible light and represents everything that transmits, filters or feels light waves (for example, a monitor, scanner or eye) (Fig. 7.5). To create different colors fold different levels Basic colors (red, green and blue). Black color is the absence of any light.

Fig. 7.5.

The image in this color model consists of three channels. When mixing basic colors, for example, blue ( IN ) And red (/?), We get an additional magenta (eng. M - Magenta. ), When mixing green ( G. ) and red ( R. ) - extra yellow (eng. Y - Yellow ), when mixing green ( G. ) and blue ( IN ) – Additional cyan (eng. C - Cyan. ). When mixing all three color components, we get white. Two electronic guns (LEDs, light filters) for red, green and blue channels are used in televisions and monitors.

Numeric display RGB.

Each of the RGB coordinates is represented as a single byte, the values \u200b\u200bof which are denoted by integers from 0 to 255 inclusive, where 0 is minimum, and 255 is the maximum intensity.

Colorref. - Standard type for presentation of colors in operating system Win32. Used to determine the color in the RGB form. Size - 4 bytes.

Determine variable type Colorref can be as follows:

ColorRefc \u003d RGB ( r, G, B ),

where g, G. and b - Intensity (ranging from 0 to 255), respectively, red, green and blue components of the color defined FROM.

Therefore, bright blue color can be defined as (0.0.255), red - like (255.0.0), bright purple - (255,0,255), black - (0,0,0), and white - (255,255,255).

IN HTML Used # RRGGGBB recording, also called hexadecimal: Each coordinate is written in the form of two hexadecimal digits, without spaces ( hTML colors See further). For example, # RRGGGBB write white - #FFFFFF.

For reference

RGB Color Space Standards.The color model RGB is dependent on the device. Since monitors different models And producers vary, several standards of color spaces were proposed for this model.

The most common SRGB color space is a standard for the image on the monitor (default profile for computer graphics). SRGB space, used with color. RGB model, has a wider color coverage on many colors (can present more saturated colors) What is the typical color space coverage of color spaces in CMYK, so sometimes images that look good in RGB are significantly duffled and goes out in CMYK.

ADOBE RGB and PROPHOTO RGB are also common. Color space Prophoto RGB, also known as ROMM RGB (from English. Reference. Output Medium Metric is a metric of an exempted output), is a RGB color space designed to process photos and an output-oriented material. The standard has been developed by the company Kodak It offers particularly wide coverage designed for photo images.

RGB is the most used color space, and it has both strong and weak sides. On the one hand, the RGB model is optimal for editing images with high resolution. It displays a wide range of values, and images in RGB format can be processed using almost all tools and functions. graphic editors .

On the other hand, RGB depends on the devices. Whatever numerical color definition, the method of its output to the screen completely depends on the display equipment.

• Graphics editor - Program (or software package), designed to create and process graphic files.