Photoshop uses threshold to adjust the color level

1. threshold principle

• The threshold value is actually a "critical point", that is, it is a situation (such as black) that does not exceed this critical point. It is another situation (such as white ), therefore, only black and white images are available. The critical point value is defined by you;
• The actual application of the threshold is to map the brightness of all pixels of a color image to the 0 ~ of the human division ~ In the 255 brightness levels, 0 is black (RGB three-color light is completely absent, so it is black), that is, the leftmost end of the threshold slider, 255 is white (RGB color light is fully superimposed, so it is white), that is, the rightmost end of the threshold slider;
• In the level dialog box, enter a value ranging from 0 ~ When the value is between 255 and 128, for example, 128, PS turns all pixels whose brightness value is less than 128 into black, and all pixels whose brightness is greater than into white, so drag them to the left to increase the white area, actually, it is to reduce the brightness value defined by the critical point pixel (you will notice that the value of the "threshold color order" is becoming smaller, so the value above this value will be more and more included in the image, and the black area is increased to the right. The brightness value defined by the critical point pixel is actually increased (the value of the "threshold level" increases ).
• Generally, it is difficult for an image to "threshold" a satisfactory contour at a time, and a white brush is needed to erase unnecessary parts.
• After understanding the principle of the threshold, we can understand the significance of increasing the contrast of the original color image. Generally, the effect is poor after the image threshold is not high.

2. Color Order Principle

The color level indicates the brightness of an image. A color level chart is a distribution chart of Different Brightness in an image. Generally, the value of the Color Order index is displayed in abscissa, and the standard scale is 0 ~ Between 255, 0 indicates no brightness, black; 255 indicates the brightest, white; and the middle is various gray. In addition, the ordinate represents the number of pixels containing "specific colors (I .e. specific levels)", so the larger the value, the more pixels in this level.

The color order diagram in PS is as follows:

Each slider indicates

A. Shadow B. Intermediate adjustment C. Highlights D. apply Automatic Color Correction

The horizontal axis indicates the brightness, and the vertical axis indicates the pixel distribution.

 

------------------------------------------------------------------------

 

You can adjust the Color comparison of an image by using the threshold and color order. For example:

1. Add the color level and threshold layer to the image

2. Adjust the threshold value to 3. The image turns white Because pixels with a brightness greater than 3 will become white.

3. Move the dark Slider of the color level until the screen displays sporadic black spots. This indicates that a small part of the screen has the shortest part and the brightness is less than 3 (sporadic black spots ),

4. Set the threshold value to 250. The image turns black because pixels with a brightness lower than 250 are black.

5. Move the color slider until there are sporadic white spots on the screen. At this time, the maximum brightness of the screen is about 250 (sporadic white spots ),

5. Remove the threshold layer and final effect