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发信人: Minatl (Minatl), 信区: Program
标  题: DELPHI 中 画 布 应 用 技 巧
发信站: BBS 荔园晨风站 (Wed Jan 20 18:54:36 1999), 转信




DELPHI 中 画 布 应 用 技 巧
辽 宁 省 铁 岭 市 气 象 局     李 莹
         在DELPHI 为 编 程 者 提 供 了 一 个 灵 活 的 绘 图 场 所, 即 本 文 所
述 的CANVAS 类, 在DELPHI 中 的 很 多 控 件 都 具 有 此 属 性, 使 编 程 者 可 以
 在 这 些 的 控 件 的 表 面 随 心 所 欲 的 绘 图, 这 对 完 善 用 户 界 面 或 者
 制 作 一 些 屏
幕 特 技 都 有 着 非 凡 的 作 用, 下 面 举 例 说 明 几 种 特 殊 屏 幕 效 果 的
形 成 过 程。

一、VANVAS 必 备 基 本 知 识：
         1. 具 有CANVAS 属 性 的 控 件:
         TBitmap ,TComboBox ,TDBComboBox ,TDBGrid ,TDBListBox ,
TDirectoryListBox ,TDrawGrid ,TFileListBox ,TForm ,THeaderControl ,TImage ,
TListBox ,TOutline ,TPaintBox ,TPrinter ,TStatusBar ,TStringGrid 等 ,
         2.CANVAS 属 性 及 命 令: 篇 幅 所 限, 省 略 参 数 及 格 式 说 明, 具 体
 请 参 考 文 后 程 序 及DELPHI 帮 助 文 件:

 canvas.rectangle(): 画 矩 形     pen.color: 定 义 画 笔 颜 色
 roundrect(): 画 圆 角 矩 形        pen.width: 定 义 画 笔 宽 度
 arc(): 画 弧 线( 不 填 充)        brush.color: 定 义 填 充 颜 色
 chord(): 画 弧 线( 填 充)        textout(): 在 固 定 位 置 输 出 字 符 串
 pie: 画 扇 形         textwidth: 取 字 符 串 高 度
 polygon(): 画 多 边 形 填 充        textheight: 取 字 符 串 宽 度
 polyline(): 多 点 连 线( 不 填 充)   font.color: 指 定 字 体 颜 色
 Pixels(): 指 定 固 定 象 素 点 颜 色 值 font.size: 指 定 字 体 大 小
 moveto(): 指 明 画 线 起 点        Ellipse(): 画 圆 或 椭 圆
 lineto(): 指 明 画 线 终 点
         3. 使 用CANVAS 注 意 事 项: 当 窗 口 进 行 重 画 时, 画 布 上 的 图 像
 将 消 失, 比 如 当 窗 口 进 行 最 小 化 又 重 新 恢 复 时， 就 会 引 起 画 布
上 图 像 的 消 失， 另 外 当 刚 刚 运 行 程 序 时， 窗 口 也 是 属 于 重 新 绘
制， 所 以 如
果 在 绘 制 窗 口 之 前 在 画 布 上 绘 图， 弹 出 窗 口 后 将 不 能 显 示 出 图
 像， 比 如 在TForm1.FormCreate() 事 件 中 进 行 画 布 绘 图 操 作 将 是 徒 劳
的， 但 可 以 在 此 事 件 中 进 行 画 布 操 作 的 准 备 工 作， 比 如 设 置 画
笔 的 颜 色 和
宽 度 等。
二、CANCAS 应 用 举 例:
         1. 为 控 件 增 加 阴 影 或 投 影 效 果: 基 本 原 理 就 是 在 利 用 该
控 件 的 父 控 件 比 如FORM 或 者 其 它 容 器 控 件 的CANVAS, 在 需 要 修 饰 的
 控 件 周 围 适 当 处 填 加 图 像, 通 过 线 条 及 颜 色 的 合 理 达 配, 使 控 件
 与 周 围 的
图 像 融 为 一 体, 形 成 特 殊 的 视 觉 效 果, 具 体 操 作 时 需 要 根 据 被 修
 饰 控 件 的TOP、LEFT、WIDTH、HEIGHT 等 属 性， 确 定 需 要 画 线 的 起 点 和 终
 点 坐 标， 这 样 操 作 无 论 被 修 饰 控 件 位 置 及 尺 寸 如 何 变 化， 都 可
 以 保 证 投
影 及 阴 影 效 果 完 美 的 实 现； 比 如 可 在 窗 口 中 建 立 三 个 按 钮, 然 后
 在 按 钮2 和 按 钮3 的CLICK 事 件 中 填 加 如 下 代 码, 之 后 按 下 按 钮2 或
按 钮3 即 使 按 钮1 形 成 投 影 和 阴 影 效 果:
procedure TForm1.Button2Click(Sender: TObject);
var
x,y,i:integer;
begin
x:=0;y:=0;
form1.canvas.pen.width:=1;
for i:=0 to 8 do
begin
form1.canvas.pen.color:=$00a0a0a0;
form1.canvas.moveto(Button1.left+Button1.width+x,
                      Button1.top+y);
form1.canvas.lineto(Button1.left+Button1.width+x,
                      Button1.top+button1.height+y);
form1.canvas.pen.color:=$00606060;
form1.canvas.moveto(Button1.left+x,
                      Button1.top+Button1.height+y);
form1.canvas.lineto(Button1.left+Button1.width+x,
                      Button1.top+button1.height+y);
x:=x+1;
y:=y+1;
end;
end;

procedure TForm1.Button3Click(Sender: TObject);
var
x,y,i:integer;
begin
x:=0;y:=0;
form1.canvas.pen.width:=1;
for i:=0 to 8 do
begin
form1.canvas.pen.color:=$00404040;
form1.canvas.moveto(Button1.left+Button1.width+x,
                         Button1.top+8);
form1.canvas.lineto(Button1.left+Button1.width+x,
                         Button1.top+button1.height+8);
form1.canvas.moveto(Button1.left+8,
                         Button1.top+Button1.height+y);
form1.canvas.lineto(Button1.left+Button1.width+8,
                         Button1.top+button1.height+y);
x:=x+1;
y:=y+1;
end;
end;
         2. 为 控 件 加 上 边 框: DELPHI 中 有 很 多 控 件 无 边 框 属 性, 利 用
CANVAS 可 以 为 任 意 的 控 件 填 加 边 框, 使 其 轮 廓 清 楚; 具 体 操 作 时,
可 先 定 义 出 画 笔 的 颜 色、 画 笔 的 宽 度( 边 框 宽 度), 之 后 用polyline()
 命 令 根 据
相 应 控 件 的 位 置、 尺 寸 自 动 定 位 四 角 坐 标， 一 次 可 完 成 一 个 固
定 宽 度 矩 形 的 绘 制 工 作， 如 果 需 要 多 种 颜 色 或 者 具 有 立 体 效 果
 的 边 框， 可 多 次 定 义 画 笔 颜 色， 画 出 连 续 的 多 个 矩 形， 通 过 调
整 相 邻 矩 形
的 颜 色 来 实 现 特 殊 效 果 的 边 框 绘 制 工 作； 比 如 在 窗 体 中 安 放 两
 个 按 钮, 分 别 在MOUSEMOVE 事 件 中 填 加 如 下 代 码, 之 后 每 当 鼠 标 移 到
 相 应 的 按 钮 上 时, 相 应 的 按 钮 就 会 出 现 特 殊 颜 色 的 边 框, 当 鼠 标
 移 到 窗 口
空 白 处 时, 则 窗 口 会 出 现 明 显 的 边 线, 起 到 特 殊 的 提 示 效 果;
procedure TForm1.Button1MouseMove
         (Sender: TObject; Shift: TShiftState; X, Y: Integer);
begin
form1.repaint;
form1.Canvas.pen.color:=clGreen;
form1.Canvas.pen.width:=5;
form1.Canvas.polyline([point(Button1.left,Button1.top),
 point(Button1.left+Button1.width,Button1.top),
 point(Button1.left+Button1.width,Button1.top+Button1.height),
 point(Button1.left,Button1.top+Button1.height),
 point(Button1.left,Button1.top)]);
end;

procedure TForm1.Button2MouseMove
             (Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
form1.repaint;
form1.Canvas.pen.color:=clBlue;
form1.Canvas.pen.width:=5;
form1.Canvas.polyline([point(Button2.left,Button2.top),
 point(Button2.left+Button2.width,Button2.top),
 point(Button2.left+Button2.width,Button2.top+Button2.height),
 point(Button2.left,Button2.top+Button2.height),
 point(Button2.left,Button2.top)]);
end;

procedure TForm1.FormMouseMove
             (Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
form1.repaint;
form1.Canvas.pen.color:=clRed;
form1.Canvas.pen.width:=3;
form1.Canvas.polyline([point(0,0), point(form1.width-10,0),
point(form1.width-10,form1.height-30),
               point(0,form1.height-30), point(0,0)]);
end;
         3. 为 图 形 按 钮 或 其 它 控 件 安 装 动 态 帮 助 功 能, 此 处 主 要
使 用 它 的 字 符 串 显 示 功 能, 也 就 是 当 鼠 标 移 到 指 定 控 件 上 时, 在
 其 周 围 适 当 位 置 显 示 相 应 的 字 符 串, 当 鼠 标 离 开 时 通 过 图 像 覆
 盖 动 作 使 字
符 串 消 失, 也 可 以 使 用 一 个 简 单 的 命 令 完 成 即form1.repaint, 它 的 作
 用 是 使FORM1 内 的 所 有 控 件 全 部 重 新 绘 制, 这 样 即 可 快 速 清 除 原
来 显 示 的 字 符; 编 程 时 主 要 使 用 各 个 控 件 的 MouseMove() 事 件; 比 如
 可 在 窗 口
中 安 放 两 个 按 钮, 并 安 排 如 下 代 码, 运 行 之 后 当 鼠 标 移 到 相 应 按
 钮 上 时, 就 会 在 其 上 方 显 示 相 应 的 提 示 信 息, 鼠 标 移 到 窗 口 空 白
 处 则 会 在 窗 口 的 左 下 角 显 示"OK" 字 样;
procedure TForm1.Button1MouseMove
     (Sender:TObject;Shift:TShiftState;X, Y: Integer);
begin
form1.repaint;
form1.Canvas.brush.color:=clGreen;
form1.Canvas.font.size:=8;
form1.Canvas.font.color:=$1200ffff;
form1.Canvas.TextOut(Button1.left,
         Button1.top-15,'OPEN FILE');
end;

procedure TForm1.Button2MouseMove
       (Sender:TObject;Shift:TShiftState;X, Y: Integer);
begin
form1.repaint;
form1.Canvas.font.size:=8;
form1.Canvas.brush.color:=clRed;
form1.Canvas.font.color:=$1200ffff;
form1.Canvas.TextOut(Button2.left,Button2.top-15,'EXIT');
end;

procedure TForm1.FormMouseMove
               (Sender:TObject;Shift:TShiftState;X,
  Y: Integer);
begin
form1.repaint;
form1.Canvas.font.size:=12;
form1.Canvas.brush.color:=clBlue;
form1.Canvas.font.color:=$00ffffff;
form1.Canvas.TextOut(0,form1.height-50,'OK');
end;
         4. 仿 电 视 移 动 字 幕 或 图 像, 用 此 方 法 制 作 移 动 字 幕 的 基
本 方 法 是: 首 先 选 定 一 个 可 作 为 画 布 的 控 件, 比 如 FORM 或IMAGE, 然
后 用 一 种 填 充 颜 色 填 满 整 个 画 布, 在 画 布 的 固 定 位 置 显 示 一 个
特 殊 前 景 色
固 定 尺 寸 的 字 符 串, 在 TIMER 控 件 中 定 时 连 续 改 变 显 示 字 符 串 的
位 置, 由 于 原 来 位 置 的 字 符 串 不 能 自 动 消 失, 所 以 需 要 用 与 填 充
 颜 色 相 同 颜 色 的 线 条 覆 盖 多 余 部 分, 这 样 即 可 实 现 平 滑 的 字 幕
 移 动 效 果;
实 现 图 像 移 动 的 方 法: 可 事 先 定 义Bitmap 类 和Rect 类 变 量, 在 程 序 运
 行 阶 段 建 立Bitmap 和Rect 对 象, 并 在Bitmap 中 装 入 指 定 的 图 像 文 件,
同 时 把 对 象Bitmap 装 入Rect 对 象 中 实 现 图 像 的 显 示, 然 后 在Timer 控
件 中 定 时 连
续 改 变Rect 的 坐 标 值, 并 用 与 填 充 颜 色 相 同 的 线 条 覆 盖 遗 留 图 像
 部 分, 即 可 以 实 现 图 像 的 平 稳 移 动; 采 用 上 述 方 法 实 现 的 字 符 串
 或 图 像 移 动 操 作, 其 效 果 平 稳， 无 任 何 闪 烁 或 抖 动 现 象， 视 觉 效
 果 极 佳，
并 且 不 需 要 事 先 建 立 控 件， 完 全 由 程 序 代 码 实 现， 具 有 相 当 多
的 优 点； 编 程 举 例: 在 窗 体 中 安 放 时 间 控 件TIMER1、 图 像 框IMAGE1, 定
 义TRECT 及TBITMAP 型 变 量, 并 在FormCreate 和Timer1Timer 事 件 中 安 排 如 下
 代 码, 程 序
运 行 之 后 即 会 在 图 像 框 中 出 现 至 下 而 上 的 移 动 字 幕 及 图 像 效 果
, 并 从 顶 部 消 失, 之 后 重 新 从 底 部 出 现;
var    { 定 义 变 量}
  Form1: TForm1;
  x,tt,l,h:integer;
  pic:Trect;
  map:Tbitmap;
{ 具 体 动 画 演 示 代 码}
procedure TForm1.Timer1Timer(Sender: TObject);
begin
x:=x-1;
tt:=tt-1;
if x<-160 then
x:=image1.height+20;
tt:=x+80;
image1.Canvas.font.size:=18;
image1.Canvas.font.color:=$1200ffff;
image1.Canvas.TextOut(10,x,'OK 字 幕 移 动 演 示');
image1.Canvas.font.size:=12;
image1.Canvas.font.color:=$120000ff;
image1.Canvas.TextOut(20,x+50,' 字 体 变 色 效 果 演 示');
l:=image1.Canvas.textwidth(' 字 体 变 色 效 果 演 示');
h:=image1.Canvas.textheight(' 字 体 变 色 效 果 演 示');
image1.Canvas.pen.color:=clGreen;
image1.Canvas.moveto(20,h+x+50-2);
image1.Canvas.lineto(20+l,h+x+50-2);
pic.topleft.x:=30;
pic.topleft.y:=tt;
pic.bottomright.x:=pic.topleft.x+100;
pic.bottomright.y:=pic.topleft.y+80;
image1.canvas.stretchdraw(pic,map);
image1.Canvas.pen.color:=clGreen;
image1.Canvas.moveto(0,pic.topleft.y+80);
image1.Canvas.lineto(pic.topleft.x+100,pic.topleft.y+80);
end;
{ 以 下 设 置 动 画 初 值}
procedure TForm1.FormCreate(Sender: TObject);
begin
timer1.enabled:=true;
timer1.Interval:=10;
x:=image1.height+20;
tt:=x+80;
form1.repaint;
image1.Canvas.brush.color:=clGreen;
pic:=Rect(0,0,image1.width,image1.height);
image1.Canvas.FillRect(pic);
pic:=Rect(-1,-1,1,1);
map:=Tbitmap.create;
map.loadfromfile('d:\windows\256color.bmp');
image1.canvas.stretchdraw(pic,map);
end;
         以 上 方 法 及 程 序 在WINDOWS95 系 统 下、DELPHI2.0 环 境 下 调 试 通
 过。




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