Pixel brightness rendering techniques for Photoshop images

　　Before you learn the contents of this chapter, be sure to hold the color basics of the lesson in front of you.

　　by learning the basics of color, we know that each pixel has a corresponding brightness, this brightness and hue is not related, the same brightness can be either red or green, as in black and white (grayscale) television, like the image of a single gray can not determine whether it is red or green. therefore, the brightness and hue of the pixel are irrelevant. It is wrong to say that green is brighter than red. We can do it. Using the third drawing method of the rectangular tool, the values of s and b are fixed by the 〖f6〗 HSB of the color palette, and only the H value is changed (note that the value of s cannot be 0%,b is 0% and 100%. Otherwise you will get the same black, white or grayscale color to pick three colors. Then create a new layer and use these three colors to draw three rectangles in the same layer. The following part of the picture.

　　Use the Go Color command: then copy and move the layer below, and then use the Go Color command "image > Adjust > Go to Color" 〖ctrl SHIFT u〗 the layer to grayscale, pull out the information palette 〖f8〗 switch to RGB, the mouse in three gray squares move, You can see that three squares have the same color. The lower part of the figure below. The arrangement of the rectangles does not need to be as neat as the image below, as long as you can see the difference. Also, if you forget how to switch the color palette and the information palette, refer to the previous course.

In fact, the brightness is similar to grayscale, gray-black and white as brightness, in the "hue-independent" aspect of the two are consistent, so gray is often used to indicate brightness. Then, convert the image to grayscale, you can see the image of the pixel brightness distribution. For example, the above-used color command "image > Adjust > Go Color" 〖ctrl SHIFT U〗, you can convert the image to grayscale. Note This sentence: "Convert the image to grayscale". This is actually not rigorous, because the go Color command does not work for all layers. So you should say, "convert layers to grayscale." In fact, the color adjustment commands are only for a single layer, even if there are layer links or layer groups.

The concept of pixel brightness: how does pixel brightness come from? In RGB mode, the pixel brightness formula is

l=rx0.3+gx0.59+bx0.11

305911 formula, from the formula can be seen, pixel brightness is different from the brightness in lab, but also different from grayscale in gray, but also different from the HSB mode of lightness, but an independent concept, only represents the brightness in RGB mode. In the next lesson we will teach you how to use PS to make the image brightness channel effect.

　　Convert an image to Grayscale color mode: If you want to convert the entire image to grayscale, change the color mode "image > Mode > Grayscale" to do so. When you change the color mode, you are prompted to merge the layers. Note that "image > Mode > Grayscale" differs from the algorithm for color-out commands. If you use image > Mode > Grayscale for the 3 colored rectangles above, you will get 3 rectangles with different shades of gray. Here we first use the effect of the color-removal command, and hue/saturation 〖ctrl U〗 to minimize the saturation of the effect as a grayscale standard. Let's look at an image in grayscale, as shown below. Because there is only one layer, you can use the Go Color command to change the entire diagram.

High/medium/dark tone of the image: Because the gray level is equal to the brightness, the grayscale image on the right of the following figure actually represents the pixel brightness in the image. Photoshop roughly divides the brightness of the image into level three: darkened, midtones, and highlights. This is a very important idea of Photoshop. The darker part of the screen is darkened, the white part belongs to the high light, and the remaining transition part belongs to the middle tune.

We know that the brightness value of the pixel is between 0 and 255, the pixel near 255 is brighter, the brightness near 0 is lower, and the remainder belongs to the middle tune. This difference in brightness is an absolute distinction between 255 pixels near the high light, 0 pixels near the darkened, and the middle tuned around 128.

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