Friday, October 06, 2006


TCanvas 這個類別是用來處理 Window 繪圖的介面, 負責與 Window 的裝置驅動程式溝通, 透過裝置驅動程式將資料顯示在顯示器上面。

C++ Builder 中, 具有 Canvas 的元件有 TForm, TImage, TbitButton ... 等等, 換句話說, 你可以在這些元件上繪圖。

TCanvas 透過畫筆 (TPen) 和 畫刷 (TBrush) 兩個類別來進行繪圖。除此, 也可以直接透過 Pixels property 對畫布上的像素色彩值進行存取。

TCanvas provides an abstract drawing space for objects that must render their own images.
TObject -> TPersistent -> TCanvas


Use TCanvas as a drawing surface for objects that draw an image of themselves. Standard window controls such as edit controls or list boxes do not require a canvas, as they are drawn by the system.

TCanvas provides properties, events and methods that assist in creating an image by
。Specifying the type of brush, pen and font to use.
。Drawing and filling a variety of shapes and lines.
。Writing text.
。Rendering graphic images.
。Enabling a response to changes in the current image.

TCanvas has two descendants, TControlCanvas and TMetafileCanvas, which assist in drawing images of controls and in creating metafile images for objects.

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