In the bitmap image there are no objects. That our eye perceives as the image of an apple, a sunset or the person of the person, actually represents the area filled with multi-colored points. If you want to move an apple on a raster picture or to color it, your task — to let know to the program that group of the points making the image of an apple on the screen, it is necessary to consider as a unit. It is necessary to select for this purpose given group of points (an image fragment) to (select). These selected points of the image we name the selected area. While in the document there is the selected area, all operations the program produces only in its limits. About the remaining (not selected) points of the image say that they are masked (i.e. are protected from changes). The data about what points of the image is selected, and what are not present, contain in a mask (it can be saved and further to use). Active (operating at a present situation) a mask is marked on the screen by a flickering circuit. This circuit we will name selection.

Selection — the major stage of editing of the bitmap image. Only after the area is selected, the user can make with it something: to reduce or increase, turn, change colors and etc. to Select the necessary group of points often uneasy. In this chapter you get acquainted with tools and selection receptions, learn to transform separation and to save them in the document, study some properties of the selected areas.

For selection in program Photoshop one is used not, and set of tools. By operation, depending on conditions, select most suitable of them or use different tools sequentially. All control instructions are collected to (Select) with selection of areas in menu Select.

The group of tools is intended for creation of selection of the correct form (fig. 3.1), disappearing for tag Rectangular Marquee (Square-topped selection). We work with them.

Open the document Things.jpg. It is on the worker to a diskette applied on the book.

Push tool Rectangular Marquee button (Square-topped selection) and from the opened group in turn select each of tools. Then again return to tool Rectangular Marquee (Square-topped selection).

Place the cursor in a document window, as is shown in fig. 3.2, and. It takes the form of cross-hairs. Push the mouse button and drag the cursor under the image. Behind the cursor the square-topped dotted selection box (fig. 3.2,) is pulled. Release the mouse button. The flickering dotted line designates boundaries of the selected area (fig. 3.2,). Install the cursor out of the selected area and construct a new selection box. The previous selection disappears and there is a new. Select tool Elliptical Marquee (Oval selection). On properties it is very similar to tool Rectangular Marquee (Square-topped selection), but is applied to elliptic areas. Try to work with this tool (fig. 3.3). For a selection canceling click the mouse in any place of a document window out of the selected area. After a canceling it is possible to return selection. For this purpose select command Reselect (to Select again) menu Select to (Select). Again cancel selection by command Deselect (to Cancel selection) the same menu.

And

As it was already told, influence of tools and the majority of commands is spread only to the selected area. We check up this statement.

Select tool Eraser (Ластик), intended for removal of fragments of the image. Cancel selection. Lead the tool under the image at a mouse pushed button. It operates as стирательная an elastic band (fig. 3.4,) Create selection. Again work as tool Eraser (Ластик). The masked sections (i.e. outside of selection) remain without changes (fig. 3.4,). And Elliptical Marquee (Oval selection) special modes of creation of a circuit of selection have tool Rectangular Marquee (Square-topped selection). They are set in the uncovered list of a property bar of the tool. These modes the following:

• Normal (Normal) — selection with the arbitrary sizes of the frame. The mode is installed by default.
• Constrained Aspect Ratio (to Save proportions) — selection of area with the given ratio of height and width which is entered in fields Width (Width) and Height (Height).
• Fixed Size (Fixed size) — creation of the frame with the exact sizes specified in fields Width (Width) and Height (Height).

Except two selection considered above tools, in this group there are two - more Single Column Marquee (column Selection) and Single Row Marquee (row Selection). They allow to define the selected area as a horizontal or vertical line in the thickness of all in one пиксел, transiting on all width or document height. The application field of such selection is very insignificant.

Creation of selection of the wrong form is produced by different methods. The second group of tools of selection is for this purpose intended. It is used much more often, than the first, and includes three tools (fig. 3.5).

Tool Lasso (Лассо) operates like a pencil. By means of it it is possible to draw any circuit on the image, and it becomes selection boundary.

1. Select tool Lasso (Лассо). Place the cursor in a document window and, pushing the mouse button, lead the tool under the image. There is a line of the future circuit of selection — you as if draw it (fig. 3.6).

2. Release the mouse button. The program creates a selection circuit on the drawn line. If the line has not been shorted, the program shorts it automatically — on a straight line.

Tool Lasso (Лассо) — not the most convenient method of selection. For creation of an exact line the solid hand is necessary. Besides, this method very labor-consuming.

If tool Lasso action (Лассо) can be compared to drawing the second tool of group by an operation principle reminds plotting. The user sets points on the image, and the program automatically builds segments of straight lines between these points. As a result the selection circuit though has the wrong form, but consists mandatory of rectilinear segments.

(fig. 3.7,).

Semi-automatic delimitation at selection

The third tool of group, Magnetic Lasso (Magnetic лассо), on action is slightly more difficult than two previous. You also draw a selection circuit, but it is allocated not precisely by the way of cursor driving. The program analyzes points of the image round the cursor at its drag and drop. It finds areas (we name their boundaries) where adjoin the points strongly differing on brightness or having different colors. On these boundaries the selection circuit also is under construction. Thus, if on the image there is a subject with contrast sections, you can select it in a semi-automatic mode very quickly, despite the difficult form. We test this tool on the suitable image.

Translate the cursor in a document window. Push a key and a cursor type changes — instead of a tool tag there will be a circle with a dagger at center. It is the exact cursor: the circle marks radius of search of boundaries, and a dagger — exact position of the tool — a flashpoint. Select tool Magnetic Lasso (Magnetic лассо) and click on a shoe circuit. You delivered the first reference point. Drift the cursor along a circuit (not very well, whether it it is pushed a mouse key) so that the circuit and a background part were in search radius. The circuit of selection in process of cursor advancement "adheres" to the most contrast boundary in a tool operative range (fig. 3.8,). Periodically the program puts reference points, fixing a selection circuit (fig. 3.8,). If there is a section dim boundary where the program cannot correctly define itself a circuit, deliver a reference point click of the mouse and continue selection in an automatic mode.

Council
If magnetic properties of the current tool hinder to create a segment of a circuit of the necessary form, it is possible to switch temporarily to tool Polygonal Lasso (Angular лассо): push ALT key and, retaining it, click the mouse. When you release ALT key, tool Magnetic Lasso (Magnetic лассо) is again activated. For switching on tool Lasso (Лассо) hold pushed ALT key and the left mouse button.

If it is necessary to delete just drawn incorrect segment (from the last reference point to the cursor), push DELETE key. Thus it is possible to delete erratic segments one after another. Short a circuit mouse double click, or pushing ALT key.

Fig. 3.8. Selection by tool Magnetic Lasso


Fig. 3.9. Control items tool Magnetic Lasso in a property bar

Tool Magnetic Lasso (Magnetic лассо) has absolutely unique for the tool of selection parameters (fig. 3.9):

• Lasso Width (Width лассо) — radius of search span of boundaries. At selection the points lying within this area are analyzed on visibility only. Make a zone big if outline area of the simple form on a monophonic background, and you should not be followed carefully on lines of boundaries, all of them will be equally found. The action radius less, the it is necessary to outline a circuit, but at обводке areas of the difficult form more carefully, motley objects it is necessary to sacrifice in the speed and to set small radius.
• Edge Contrast (Contrast of boundaries) — sensitivity parameter. Defines, to what level two points of the image that the program counted as their boundary should differ. Great values are applied at selection of contrast areas, small — at small contrast.
• Frequency (Frequency of points) — frequency of setting of reference points on a selection circuit. Than the boundary and the more difficult the form of selected area is less expressed, the above there should be a value of this parameter.

Selection of areas with the close colors

It is necessary to tell about one tool of selection Magic Wand (Magic wand) possessing special characteristics. Unlike other tools, it is intended for automatic creation of selection. The principle of its action consists in selection of relatives lying nearby on color of points of the image (пикселов). Thus a threshold of proximity of color (tolerance) you can set in the field Tolerance property bar (Threshold) (fig. 3.10). It is very useful tool, and to work with it easily and pleasantly.

Fig. 3.10. Tool Magic Wand Property bar

Open the document Acropol.jpg. Let it is necessary to select a background round a building. Despite apparent complexity, the task dares simply enough.

Select tool Magic Wand (Magic wand) and click on the upper part of the sky (fig. 3.11,). The background most part (fig. 3.11,) is selected. Retaining pushed SHIFT key, click on even not selected part of a background. Thus add to the first selection all remaining sections of the image, except for concerning a building.

The remark
Note that the program calculates the close colors, proceeding from color пиксела in a mouse click point. Therefore the selection form can differ, depending on in what point you clicked.

Whether it is possible to select with one click all background? In this case it is possible, it is necessary to increase only a threshold that the program carried to relatives большее number of shades.

Fig. 3.11. Tool Magic Wand type () and selection of area depending on value of a threshold (б—г)

Increase value of parameter Tolerance (Threshold) and again click on the image. Regulate a threshold and specify a click place until the background will not be selected at once (fig. 3.11, in,).

Note that at selection there is not selected a section of a background in object (fig. 3.12,) as it is separated from a remaining background by others on color пикселами. Removal of flag Contiguous (Continuously) in a property bar (fig. 3.10) allows to cope with this problem. By default it is installed, and then the choice of the close colors is produced only in boundary with a point of click areas. It is necessary to remove a flag, and relatives on color of area are selected from limits of all image. We try to select all background one click of the mouse.

Remove flag Contiguous (Continuously).

Click again against the image. All areas of a background, including a section in object (fig. 3.12,) are selected.

Fig. 3.12. Selection at installed () and removed () flag Contiguous

In menu Select (Selection) there is special command Color Range (a color Choice) for selection of areas, close on color. As for selection creation this command uses concept of a mask, we consider it later.

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