We often hear some image processing terms, such as digital photos, image operations, mixing modes, etc., but beginners often fail to understand their meaning during the production process. Especially when learning mixed mode, I often feel at a loss when faced with unfamiliar and difficult teaching materials.
In this lesson, we will explore a small area of number operations - cutting out images using mixed modes.
Cai Cai: Mixing modes are really difficult to learn. I was dazzled when I saw some learning materials listing a long row of working styles. Others posted a few pictures, saying that this blend would be darker and that blend would be lighter. It seems that I don't know what it is used for.
Teacher Qi: The mixing mode is indeed difficult to learn. Some friends will pull out complicated formulas to explain, but that is too unintuitive, and if you use photo overlay to understand it, you cannot understand its changing rules. From my point of view, beginners should pay more attention to the study of the rules of mixing modes. As long as they understand what results will be obtained by mixing two pictures in a certain mode, the key is to apply what they have learned. The work of deriving formulas is left to mathematics. Do it at home.
The books recommended here that explain unique mixing modes are the "Art of Selection" series of books published by People's Posts and Telecommunications Publishing House, written by Mr. Guan Wentao, which are very suitable for in-depth research on image synthesis. If you like video explanations, you can take a look at the "Photoshop Expert Lecture" CD produced by me to establish a more intuitive understanding of blending modes.
Tools and techniques used in this issue: blending modes, masks.
Knowledge reserve before cutting out pictures - understanding color screening and multiplication modes
Three feet of ice cannot be frozen in a day. Knowledge needs to be accumulated bit by bit. Learning hybrid mode requires a lot of content, and explaining it requires considerable time and patience. In this lesson we are learning the mixed mode cutout method, so we choose an intuitive method to explain - the experimental comparison method.
Let’s look at the first picture. This is a layered picture I made in advance. Below is a picture. On the upper layer we put a gradient color block, which is black at the top, white at the bottom and gray in the middle. The color has a smooth transition. Let's name this layer "Test Layer".
We first need to take a look at the changes that occur to the image when we apply layer blending to it. After analyzing the changes, we can apply it in practice.
Set the blending mode of the test layer to "Multiply" (marked 1) on the layer panel. We can see that the white part of the test layer disappears immediately! Only black is left in the transitional part between black and white, and the white background is completely removed.
We can understand it this way. The test layer is like a piece of white paper, with black drawn on it. Later, after we apply the Multiply blending mode, the black color is retained, and the white drawing paper is completely cleared and becomes Creates the effect of painting on a transparent canvas. This cannot be achieved by using the selection area to cut out the image!
We then change the blending mode to "Screen" (marked 2), and the image immediately changes. The white is retained and the black is removed. From here we can see that Multiply and Filter are two corresponding mixing modes, just like the relationship between the left hand and the right hand, contradictory yet unified.
As can be seen from the above experiment, the multiply mode can be used to extract black hair on a light background, and the filter mode can be used to extract a white wedding dress on a dark background. If we use these two modes together, we can also cut out the highlights and shadows of the glass bottle to get a transparent glass bottle effect.
Use blending modes to cut out hair
We have done basic experiments, let's get down to business and see how to apply hybrid mode in practice
Let's take a look at this picture again. If we look closely at the hair part, we can see that the contrast between the hair and the surrounding background is great. The hair part is very dark, and there will be a faint transition color at the junction of the hair and the background. If we use the selection tool to pick it out , the complex edge shape will make the operation very painful, and after the picking is completed, there will still be a very ugly gray edge. If we use the Multiply blending mode to extract, we won’t have this problem!
1. Place the character image on the background image. In this example, we use a landscape photo as the background to test the cutout effect. You can see the background layer in the layers panel.
On the character layer, press Ctrl+J to make a copy of it. We will use two character layers to form the final cutout character image.
2. Click the eye icon shown at mark 1 to hide the top character layer. Click on the "People" layer and set the blending mode of this layer to Multiply mode, as shown by mark 2.
The image immediately changed dramatically. The white background of the character image was removed, and the background behind it was revealed. Through observation, we can find that for a layer set to Multiply, the brighter pixels will become transparent, and the darker pixels will be combined with the underlying image.
It is precisely because of this feature of multiplication that the darker hair is picked out very cleanly. However, because the color of the character's face is brighter, it has also become transparent. This is not the effect we want, so in the next step we will use the mask to cut out the character copy layer, and combine the two layers to cut out the character.
3. Click the eye icon in front of the character copy layer to display it. Click this layer to enlarge the image and use the polygon selection tool to select the main part of the character. Click the Add Layer Mask button below the Layers panel to convert it into a mask. The transparency phenomenon inside the character will be corrected immediately. This is the multi-layer combined cutout method. We can cut out each part of the image separately, and finally stack multiple layers together to form the result image.
But now a new problem has emerged. When we observe the joint part of the hair in the two layers, we can find that their fusion is not ideal and has a very stiff joint edge. This is because after the Multiply layer is mixed with the lower layer, the hair becomes darker, and the image on the upper layer is obviously different from the image on the lower layer, so a sharp edge appears.
