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gdi programming with c sharp phần 4

Lớp Graphics cung cấp nhiều hơn chỉ cần vẽ và điền vào các phương pháp. Phương pháp hỗn hợp được quy định trong Bảng 3.6. Một số những phương pháp này sẽ được thảo luận chi tiết hơn sau này.Phương pháp Clear xóa toàn bộ bề mặt vẽ và điền vào nó với màu nền theo quy định. Phải mất một đối số, loại màu. | This document was created by an unregistered ChmMagic please go to http www.bisenter.com to register it. Thanks Team LiB 4 PREVIOUS NEXT 4.6 A Real-World Example Adding Colors Pens and Brushes to the GDI Painter Application In Chapter 3 we created the GDI Painter application which allows us to draw simple objects such as a line a rectangle and an ellipse. In this section we will extend the functionality of GDI Painter by adding support for brushes and pens. After completing this section you will be able to select a pen color and its width color transparency and brush color. Figure 4.32 shows the modified version of GDI Painter without any objects. Figure 4.32. GDI Painter with pen and brush support Transparency is a component of the color in GDI . In the .NET Framework library th Color structure represents a color. It has four components alpha A red R green G and blue B . The alpha component of the Color structure represents the transparency of a color. The alpha component values vary from 0 to 255 where 0 is fully transparent and 255 is fully opaque. To create a transparent brush or pen we create a color using the alpha value and use the color to create a pen or a brush. We will discuss colors and alpha transparency in more detail in Chapter 5 ARGB is the focus of Section 5.2 . This document was created by an unregistered ChmMagic please go to http www.bisenter.com to register it. Thanks The following code snippet shows how to create a color with transparency. We use the same method to add transparency to our application. Color clr Color.FromArgb Convert.ToInt16 TransCounter.Value.ToString PenBtn.BackColor.R PenBtn.BackColor.G PenBtn.BackColor.B In our modified version of GDI Painter the width selector numeric up-down control allows you to select the width of the pen. A pen is used when we draw the outlines of graphics shapes. A brush is used when we draw filled graphics shapes. The Pen color and Brush color buttons launchColorDialog which lets us select a color .