Anti-aliasing and feathering

We use the elliptical marquee tool to turn off and turn on anti-aliasing (also known as anti-aliasing), create two roughly large, rounded selections, and then fill the black look. How to quickly fill black do you remember? First 〖x〗 and then 〖alt Delete〗. After the fill deselect 〖ctrl D〗, the effect is shown below.

Careful observation of the edges of the two circles, you will see the first round of the edge is more blunt, there are obvious ladder-like, also called Sawtooth. The second circle has a relatively smooth look.

In the previous course #02 we have studied the causes of sawtooth, which is caused by the characteristics of the lattice image. Because the dot image uses a small square point to describe the image, it produces a jagged line when describing the curve and some angles.

Then why does the second circle have no sawtooth? No, really? Let's enlarge the image by the space CTRL click some to see. The following figure.

You can see that the second circle is actually jagged, but the edges of the sawtooth become softer. There is a transition effect from black to background white. So it looks a little smoother than the first round. This is the effect of anti-aliasing. So the so-called anti-aliasing is not really eliminated, but only the use of "camouflage" to make the image look smooth. As long as the image is lattice, the sawtooth will always exist.

The vector image is not jagged in theory, but because the physical properties of the display are also dot matrix, the vector image will also have a sawtooth phenomenon when it is finally displayed on the screen.

The sawtooth of the lattice image is caused by the combination of the image format and the physical characteristics of the display. The sawtooth of a vector image is caused only by the physical characteristics of the display. Although the two appear to be consistent in some cases, as we have learned before, the jagged edges of the dot-matrix image are reduced or magnified during the scaling of the image, and the sawtooth of the vector image does not scale.

If you are careful, you will find that the rectangles, single-line, and single column marquee tools have no anti-aliasing options. Why, then? Think for yourself. The answer is at the end of this section.

What do you think about feathers? is a kind of soft feeling. The feather option also works. Now use the elliptical Marquee tool, set the feather to 0 and 5, draw two positive circle selections, and then fill the color, and do not cancel the selection. The effect is shown below. When you see a 5-pixel feather, the color of the fill is no longer within the dotted box of the selection, but it extends beyond the selection and renders a fading effect.

As you can see, this fading effect centers on the dotted line of the selection and extends both inside and outside the selection. The following figure.

This time, if you use a 10-pixel brush tool and choose a red color to draw in the selection, you will get the effect of the following figure.

As we said earlier, when a selection is established, almost all operations are only valid for the selection, but why is the brush now available outside the dotted box of the selection? Also, the previously populated black is not entirely within the constituency, and some of it exceeds the dotted line of the selection.

This is because the dotted box of a selection sometimes does not fully represent the selected range, and this question is explained later in this chapter.

The feather option's role is to blur the edges of the selection so that you get a softer transition when making the compositing effect. Now open the following 2 image in Photoshop.

Set the feather to 0, use the Lasso tool to roughly select the middle flower, and then select the Move tool on the toolbar (Ctrl can also be temporarily switched to the Move tool when you create a selection using the selection tool) and move to another image within the selection. The following figure. This is how Photoshop supports dragging content directly between open images. The starting image you drag is called the source image, and the image you drag to is called the target image.

Note that when the cursor is displayed in the selection, dragging is the image in the selection, and if the cursor is displayed outside the selection, the entire image will be dragged. Should be seen clearly to avoid misoperation.

After the drag completes the effect is as follows left picture. You can see the edge of the image dragged over is more blunt. Now press F12 to restore the target image to its original state. Then switch to the original image, also press F12 restore. F12 is to restore the image to its last saved state.

Set the feather to 5, and repeat the above procedure. You can see the edges of the flowers in this target image appear much softer. The following is the right figure.

Although the selection tool provides a direct feather option in the public column, it is not recommended to use it directly. Because the selection feather effect is not satisfactory, the selection disappears after you undo one step 〖ctrl ALT Z〗. To re-create a selection after changing the feather value.

It is recommended that you set feather to 0 when you are done, and then use the menu "SELECT > Feather" 〖ctrl ALT D〗 When you are finished, or right-click (under the premise of the selection tool or trimming tool) to select feather in the menu that appears, the following Feather Settings dialog box appears. Then enter the value and return. The feather effect is the same as it was previously set in the public column.

The advantage of this is that if you find the degree of feathering unsatisfactory, you can undo the 〖ctrl ALT Z〗 and reset the feather values without causing the original selection to disappear. The feather that is mentioned in later content is the way to create and then feather first.

When feathering is set, the selection dashed box may shrink and the corners will become smooth, and the following left figure is the effect of feathering 10 pixels. If you enter a value that is too large for the feather, you may receive a warning from the following right figure, while the selection dash disappears. The dotted box narrows and the reason for the warning after the big feather, everyone in the later content will be answered.

As you can see, feathering renders the edges of the selected image similar to translucent, which facilitates the synthesis of effects in different images. But the effect of feathering is actually not ideal, because the effect of feathering is evenly distributed along the edge of the selection. And most of the time we need to set different levels of transparency or feathering in different places. Therefore, there are fewer opportunities to use feathering directly.

Now to answer one of the previous questions: Why doesn't the rectangle, Single-line, and single column marquee tool have anti-aliasing options? That's because the selection edges created by these 3 selection tools must be horizontal or vertical, with no curves or slashes. The sawtooth only appears in curves or slashes. The 3 selection tools do not have anti-aliasing options because they do not produce jagged edges at all.

In the course #03 we have learned the drawing tool brush, the brush set has a hardness, change the hardness can make the edge of the brush to soften, this soft effect is actually a feather effect.

There is also a pencil tool in combination with the brush tool. The edge of the pencil tool is blunt and always has a jagged effect. The other settings and brush tools are the same.

Note that although there are also hardness options in the pencil setting, there is no brush that changes the edge softness. The biggest difference between a pencil and a brush is that the pencil has no edge feather, so it looks more stiff. The following figure left and right two maple leaf and wavy line effect contrast.