代码下载：
https://download.csdn.net/download/zhujianqiangqq/12394579
代码实例：
1 unit Unit1;
2
3 interface
4
5 uses
6 System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
7 FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.Objects,
8 FMX.Controls.Presentation, FMX.StdCtrls, FMX.Edit;
9
10 type
11 TCanvasData = record //定义绘制数据数组
12 //画笔可设置的参数
13 PenStartSize: Integer; //画笔开始大小
14 PenMinSize: Integer; //画笔最小大小
15 PenMaxSize: Integer; //画笔最大大小
16 PenMobileBorder: Integer; //移动界限，超过这个值就改变笔大小值
17 PenChangeValue: Integer; //画笔每次改变的大小
18 PenSizeChangeSpeed: Integer;//笔的改变速度，越小改变的速度越快
19 //画图用到的参数
20 PenCurrentSize: Integer; //画笔当前大小
21 PenLastPoint: TPointF; //画笔最后的点
22 PenMobileDistance: TPointF; //画笔移动了多少距离
23 MouseDownTab:Boolean; //鼠标按下标记
24 Yadd:Integer;
25 end;
26
27 TForm1 = class(TForm)
28 IMOriginal: TImage;
29 IMCanvas: TImage;
30 Paint: TPanel;
31 operate: TPanel;
32 Label1: TLabel;
33 Label2: TLabel;
34 Label3: TLabel;
35 Label4: TLabel;
36 Label5: TLabel;
37 Label6: TLabel;
38 LEPenStartSize: TEdit;
39 LEPenMinSize: TEdit;
40 LEPenMaxSize: TEdit;
41 LEPenMobileBorder: TEdit;
42 LEPenChangeValue: TEdit;
43 LEPenSizeChangeSpeed: TEdit;
44 Timer1: TTimer;
45 Button1: TButton;
46 procedure IMCanvasMouseDown(Sender: TObject; Button: TMouseButton;
47 Shift: TShiftState; X, Y: Single);
48 procedure IMCanvasMouseMove(Sender: TObject; Shift: TShiftState; X,
49 Y: Single);
50 procedure FormCreate(Sender: TObject);
51 procedure IMCanvasMouseUp(Sender: TObject; Button: TMouseButton;
52 Shift: TShiftState; X, Y: Single);
53 procedure Timer1Timer(Sender: TObject);
54 procedure LEPenStartSizeChange(Sender: TObject);
55 procedure FormResize(Sender: TObject);
56 procedure Button1Click(Sender: TObject);
57 private
58 { Private declarations }
59 public
60 { Public declarations }
61 end;
62
63 var
64 Form1: TForm1;
65 MYCanvasData: TCanvasData;//定义画笔数据变量
66
67 implementation
68 uses
69 System.UIConsts;
70
71 {$R *.fmx}
72 {$R *.LgXhdpiPh.fmx ANDROID}
73
74 procedure TForm1.LEPenStartSizeChange(Sender: TObject);
75 begin
76 MYCanvasData.PenStartSize := StrToInt(LEPenStartSize.Text); //开始笔头大小
77 MYCanvasData.PenMinSize := StrToInt(LEPenMinSize.Text); //最小笔头
78 MYCanvasData.PenMaxSize := StrToInt(LEPenMaxSize.Text); //最大笔头
79 MYCanvasData.PenMobileBorder := StrToInt(LEPenMobileBorder.Text); //移动距离 超过值时 改变笔头大小
80 MYCanvasData.PenChangeValue := StrToInt(LEPenChangeValue.Text); //每次大小变动的单位
81 MYCanvasData.PenCurrentSize := StrToInt(LEPenSizeChangeSpeed.Text); //笔头 大小 改变的速度 越小速度越快
82 end;
83
84 procedure TForm1.Button1Click(Sender: TObject);
85 begin
86 IMCanvas.Bitmap := nil;
87 IMCanvas.Bitmap.SetSize(Round(IMCanvas.Width), Round(IMCanvas.Height));
88 end;
89
90 procedure TForm1.FormCreate(Sender: TObject);
91 begin
92 IMOriginal.SendToBack;
93
94 LEPenStartSize.Text := '5';
95 LEPenMinSize.Text := '4';
96 LEPenMaxSize.Text := '10';
97 LEPenMobileBorder.Text := '5';
98 LEPenChangeValue.Text := '1';
99 LEPenSizeChangeSpeed.Text := '3';
100
101 MYCanvasData.PenStartSize := 5;
102 MYCanvasData.PenMinSize := 4;
103 MYCanvasData.PenMaxSize := 10;
104 MYCanvasData.PenMobileBorder := 5;
105 MYCanvasData.PenChangeValue := 1;
106 MYCanvasData.PenSizeChangeSpeed := 3;
107
108 LEPenStartSize.OnChange := LEPenStartSizeChange;
109 LEPenMinSize.OnChange := LEPenStartSizeChange;
110 LEPenMaxSize.OnChange := LEPenStartSizeChange;
111 LEPenMobileBorder.OnChange := LEPenStartSizeChange;
112 LEPenChangeValue.OnChange := LEPenStartSizeChange;
113 LEPenSizeChangeSpeed.OnChange := LEPenStartSizeChange;
114
115 IMCanvas.Bitmap.SetSize(Round(IMCanvas.Width), Round(IMCanvas.Height));
116 // IMCanvas.Bitmap.Clear(TAlphaColors.White);
117 end;
118
119 procedure TForm1.FormResize(Sender: TObject);
120 begin
121 IMCanvas.Bitmap.SetSize(Round(IMCanvas.Width), Round(IMCanvas.Height));
122 end;
123
124 procedure TForm1.IMCanvasMouseDown(Sender: TObject; Button: TMouseButton;
125 Shift: TShiftState; X, Y: Single);
126 begin
127 case Button of
128 TMouseButton.mbLeft:
129 begin
130 MYCanvasData.PenCurrentSize := MYCanvasData.PenStartSize;
131 MYCanvasData.PenMobileDistance.X := -1;
132 MYCanvasData.PenLastPoint.X := X;
133 MYCanvasData.PenLastPoint.Y := Y;
134 //Yadd:=1;
135 MYCanvasData.MouseDownTab := True;
136 end;
137 TMouseButton.mbRight: ;
138 TMouseButton.mbMiddle: ;
139 end;
140 end;
141
142 procedure TForm1.IMCanvasMouseMove(Sender: TObject; Shift: TShiftState; X,
143 Y: Single);
144 var
145 p1, p2: TPointF;
146 begin
147 Form1.Caption:='当前笔头大小:' + IntToStr(MYCanvasData.PenCurrentSize);
148 if MYCanvasData.MouseDownTab then
149 begin
150 IMCanvas.Bitmap.Canvas.BeginScene;
151 IMCanvas.Bitmap.Canvas.Stroke.Thickness := MYCanvasData.PenCurrentSize;
152 IMCanvas.Bitmap.Canvas.Stroke.Cap := TStrokeCap.Round;
153
154 p1 := TPointF.Create(MYCanvasData.PenLastPoint.X, MYCanvasData.PenLastPoint.Y);
155 p2 := TPointF.Create(X, Y);
156
157 IMCanvas.Bitmap.Canvas.DrawLine(p1, p2, 100);
158 IMCanvas.Bitmap.Canvas.EndScene;
159
160 MYCanvasData.PenLastPoint.X := X;
161 MYCanvasData.PenLastPoint.Y := Y;
162 end;
163 end;
164
165 procedure TForm1.IMCanvasMouseUp(Sender: TObject; Button: TMouseButton;
166 Shift: TShiftState; X, Y: Single);
167 begin
168 case Button of
169 TMouseButton.mbLeft: MYCanvasData.MouseDownTab := False;
170 TMouseButton.mbRight:;
171 TMouseButton.mbMiddle:;
172 end;
173 end;
174
175 procedure TForm1.Timer1Timer(Sender: TObject);
176 begin
177 if MYCanvasData.MouseDownTab then
178 Begin
179 if MYCanvasData.PenMobileDistance.X > -1 then
180 begin
181 Inc(MYCanvasData.Yadd);
182 if (Abs(MYCanvasData.PenMobileDistance.X - MYCanvasData.PenLastPoint.X) < MYCanvasData.PenMobileBorder) and
183 (Abs(MYCanvasData.PenMobileDistance.Y - MYCanvasData.PenLastPoint.Y) < MYCanvasData.PenMobileBorder) then
184 Begin
185 if (MYCanvasData.Yadd >= MYCanvasData.PenSizeChangeSpeed) then
186 if (MYCanvasData.PenCurrentSize < MYCanvasData.PenMaxSize) then
187 begin
188 MYCanvasData.PenCurrentSize := MYCanvasData.PenCurrentSize + MYCanvasData.PenChangeValue;
189 MYCanvasData.Yadd:=1;
190 end;
191 end
192 else
193 begin
194 if (MYCanvasData.Yadd >= MYCanvasData.PenSizeChangeSpeed) then
195 if (MYCanvasData.PenCurrentSize > MYCanvasData.PenMinSize) then
196 begin
197 MYCanvasData.PenCurrentSize := MYCanvasData.PenCurrentSize - MYCanvasData.PenChangeValue;
198 MYCanvasData.Yadd := 1;
199 end;
200 end;
201 end;
202 MYCanvasData.PenMobileDistance.X := MYCanvasData.PenLastPoint.X;
203 MYCanvasData.PenMobileDistance.Y := MYCanvasData.PenLastPoint.Y;
204 End;
205 end;
206
207 end.
来源：oschina
链接：https://my.oschina.net/u/4272135/blog/4268925