The Shapes Library panel manages libraries of reusable shapes. You can create your own libraries, save shapes, and reuse them throughout multiple projects. Graphic includes a few built-in example libraries to help you get started.

Graphic For Mac Shape Library For Mac

The gfx library only requires that the programmer understand how to invoke basic C functions with scalar arguments. It is more than enough to explore raster and vector graphics, create animations, draw fractal shapes, and write simple video games. It doesn't do everything that you might want a graphics.
By the way, custom shapes were introduced in the 6th Photoshop edition, they allow you do much more with vector graphics than a pen tool. Photoshop custom shapes are very useful, if you do not have an appropriate brush you can use a readymade custom shape preset.

A graphics context represents a drawing destination. It contains drawing parameters and all device-specific information that the drawing system needs to perform any subsequent drawing commands. A graphics context defines basic drawing attributes such as the colors to use when drawing, the clipping area, line width and style information, font information, compositing options, and several others.

You can obtain a graphics context by using Quartz context creation functions or by using higher-level functions provided by one of the Mac OS X frameworks or the UIKit framework in iOS. Quartz provides functions for various flavors of Quartz graphics contexts including bitmap and PDF, which you can use to create custom content.

This chapter shows you how to create a graphics context for a variety of drawing destinations. A graphics context is represented in your code by the data type CGContextRef, which is an opaque data type. After you obtain a graphics context, you can use Quartz 2D functions to draw to the context, perform operations (such as translations) on the context, and change graphics state parameters, such as line width and fill color.

Drawing to a View Graphics Context in iOS

To draw to the screen in an iOS application, you set up a UIView object and implement its drawRect: method to perform drawing. The view’s drawRect: method is called when the view is visible onscreen and its contents need updating. Before calling your custom drawRect: method, the view object automatically configures its drawing environment so that your code can start drawing immediately. As part of this configuration, the UIView object creates a graphics context (a CGContextRef opaque type) for the current drawing environment. You obtain this graphics context in your drawRect: method by calling the UIKit function UIGraphicsGetCurrentContext.

The default coordinate system used throughout UIKit is different from the coordinate system used by Quartz. In UIKit, the origin is in the upper-left corner, with the positive-y value pointing downward. The UIView object modifies the CTM of the Quartz graphics context to match the UIKit conventions by translating the origin to the upper left corner of the view and inverting the y-axis by multiplying it by -1. For more information on modified-coordinate systems and the implications in your own drawing code, see Quartz 2D Coordinate Systems.

UIView objects are described in detail in View Programming Guide for iOS.

Creating a Window Graphics Context in Mac OS X

When drawing in Mac OS X, you need to create a window graphics context that’s appropriate for the framework you are using. The Quartz 2D API itself provides no functions to obtain a windows graphics context. Instead, you use the Cocoa framework to obtain a context for a window created in Cocoa.

You obtain a Quartz graphics context from within the drawRect: routine of a Cocoa application using the following line of code:

The method currentContext returns the NSGraphicsContext instance of the current thread. The method graphicsPort returns the low-level, platform-specific graphics context represented by the receiver, which is a Quartz graphics context. (Don’t get confused by the method names; they are historical.) For more information see NSGraphicsContext Class Reference.

After you obtain the graphics context, you can call any of the Quartz 2D drawing functions in your Cocoa application. You can also mix Quartz 2D calls with Cocoa drawing calls. You can see an example of Quartz 2D drawing to a Cocoa view by looking at Figure 2-1. The drawing consists of two overlapping rectangles, an opaque red one and a partially transparent blue one. You’ll learn more about transparency in Color and Color Spaces. The ability to control how much you can “see through” colors is one of the hallmark features of Quartz 2D.

To create the drawing in Figure 2-1, you first create a Cocoa application Xcode project. In Interface Builder, drag a Custom View to the window and subclass it. Then write an implementation for the subclassed view, similar to what Listing 2-1 shows. For this example, the subclassed view is named MyQuartzView. The drawRect: method for the view contains all the Quartz drawing code. A detailed explanation for each numbered line of code appears following the listing.

Note: The drawRect: method of the NSView class is invoked automatically each time the view needs to be drawn. To find out more about overriding the drawRect: method, see NSView Class Reference.

Listing 2-1 Drawing to a window graphics context

Here’s what the code does:

Obtains a graphics context for the view.
This is where you insert your drawing code. The four lines of code that follow are examples of using Quartz 2D functions.
Sets a red fill color that’s fully opaque. For information on colors and alpha (which sets opacity), see Color and Color Spaces.
Fills a rectangle whose origin is (0,0) and whose width is 200 and height is 100. For information on drawing rectangles, see Paths.
Sets a blue fill color that’s partially transparent.
Fills a rectangle whose origin is (0,0) and whose width is 100 and height is 200.

Creating a PDF Graphics Context

When you create a PDF graphics context and draw to that context, Quartz records your drawing as a series of PDF drawing commands written to a file. You supply a location for the PDF output and a default media box—a rectangle that specifies bounds of the page. Figure 2-2 shows the result of drawing to a PDF graphics context and then opening the resulting PDF in Preview.

The Quartz 2D API provides two functions that create a PDF graphics context:

CGPDFContextCreateWithURL, which you use when you want to specify the location for the PDF output as a Core Foundation URL. Listing 2-2 shows how to use this function to create a PDF graphics context.
CGPDFContextCreate, which you use when you want the PDF output sent to a data consumer. (For more information see Data Management in Quartz 2D.) Listing 2-3 shows how to use this function to create a PDF graphics context.

A detailed explanation for each numbered line of code follows each listing.

iOS Note: A PDF graphics context in iOS uses the default coordinate system provided by Quartz, without applying a transform to match the UIKit coordinate system. If your application plans on sharing drawing code between your PDF graphics context and the graphics context provided by UIView object, your application should modify the CTM of the PDF graphics context to modify t