Work with layers. The overlay option “Overlay if:”
Most projects require editing multiple images. Nevertheless, only those images that are extracted “purely” from the general background can be effectively used. In this lesson, we will look at the method of extracting an object using the overlay parameter “Overlay if:” (“Blend If:”).
We need to extract the model from the background. Duplicate the layer (CTRL + J) as “Layer 1”.
Then, create a “Layer 2” and place it under “Layer 1”. Fill “Layer 2” with a bright blue background. This “blue screen” will help us in identifying the necessary and unnecessary areas.
Double click on “Layer 1”, the Layer Style menu will appear. Let us dwell on the blending options option “Overlay if:” (Blending Options> Blend If
Pay attention to the gradient scale with values from 0 to 255 (0 is the darkest point; 255 is the brightest point) and sliders at each end. Choosing “Overlay if: Gray” (“Blend If: Gray”) allows us to use grayscale as the base for the overlay.
When you drag the left slider to the right to the value of 50, a blue background appears (the dark parts of the image become transparent).
When you move the white slider, the light areas of the image become transparent.
But the area stands out roughly, not exactly, and we want to achieve a smooth transition.
While holding ALT share the engine. Setting the interval, we soften the border between the light and dark areas of the selected area. The interval between the separated engines will determine the transparency of these areas.
In this example, the parameters are set to 90/190. The area around the hair becomes more transparent (a blue background appears).
Next, duplicate the “Layer 1”. Double-click on the copy of layer 1, call the option of blending parameters and restore the sliders on the “Overlay if:” scale. Add a mask to the layer and fill it with black.
Then, choose a brush (brush) and white “clean” the face, skin and areas that we need. Do not leave a hint of blue color on the desired areas, otherwise “holes” may form.
When done, hold CTRL and select “Layer 1” and merge it with the working layer (CTRL + E). The image is ready to use.
Note: Before merging, make sure that the resulting image is what you need. If you are not satisfied with the result, still work with the overlay parameters.
This method may not always be used effectively. A region with white edges would be difficult to distinguish from a light background due to low contrast.
Images with higher contrast ratios are easier to manipulate using the “Overlay if:” option.
In order to determine which area of the image has a higher contrast ratio, it is necessary to call the Channels Window (Windows> Channel).
In the tree example, the blue channel is selected. Of the 3 channels, blue shows the greatest contrast between the object (tree) and the background (sky). Use the blue channel as the base for this image.
From the blending options, select in “Overlay if:” Blue. We are going to clean the bright part of the channel.
Holding ALT, we separate and drag the engines (select interval 70/200). For better visibility, we use a bright red background. Move the engines until the sky is almost transparent with a smooth transition.
Along the edges of the tree still remain “traces” of the sky. It is unlikely that it will be possible to isolate it purely from the first time, so – experiment!
Press CTRL + U to bring up the Hue / Saturation window. Select the Blue editing (Cyan) and reduce the saturation to -75.
Create an empty layer and merge it with the working layer. Thus, we align the “clean” edges of the object and the “remnants” of the previous background.
In addition to fine-tuning Color Hue / Saturation, you can use Color Balance and Selective Color. You can even use a layer mask for a more dramatic overlay of an object on a new layer.
The “Underlying Layer” option works in the same way.
Place the female portrait layer above the facade image with windows.
Using Free Transformation (CTRL + T), “adjust” the female portrait to the perspective of the facade.
It is necessary to show the sash windows in the upper layer (model). To do this, drag the left engines to show the dark areas of the layer, and the right to show the light. Use the blue channel again to achieve the desired result.
Add clouds to the face of the model. Then merge all the layers.