BGRABitmap tutorial 1: what changed

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Old	New		Line
1	1		This first tutorial shows you how to use [[BGRABitmap]] library.
2	2
3	3		You can download the library on [GitHub](https://github.com/bgrabitmap).
4	4
5	5		### Create a new project
6	6
7	7		Create an windowed application with menu Project \> New project.
8	8
9	9		The main form unit should look like this:
10	10
11	11		``` pascal
12	12		unit UMain;
13	13
14	14		{$mode objfpc}{$H+}
15	15
16	16		interface
17	17
18	18		uses
19	19		Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs;
20	20
21	21		type
22	22
23	23		{ TForm1 }
24	24
25	25		TForm1 = class(TForm)
26	26		private
27	27		{ private declarations }
28	28		public
29	29		{ public declarations }
30	30		end;
31	31
32	32		var
33	33		Form1: TForm1;
34	34
35	35		implementation
36	36
37	37		initialization
38	38		{$I UMain.lrs}
39	39
40	40		end.
41	41		```
42	42
43	43		If you do not find it, use Ctrl-F12 to show file list.
44	44
45	45		Save your project next to BGRABitmap library with menu File \> Save all (not necessarily in the same folder).
46	46
47	47		### Add reference to BGRABitmap
48	48
49	49		The first time you use BGRABitmap, open bgrabitmappack.lpk with Lazarus and click on "Use \> Add to Project". Then, if you need to add the reference in another project, you can do it through the Project inspector and click on "Add... \> New condition" and choose BGRABitmapPack.
50	50
51	51		In the unit clause, add a reference to BGRABitmap and BGRABitmapTypes after Dialogs.
52	52
53	53		``` pascal
54	54		uses
55	55		Classes, SysUtils, FileUtil, LResources,
56	56		Forms, Controls, Graphics, Dialogs,
57	57		BGRABitmap, BGRABitmapTypes;
58	58		```
59	59
60	60		#### Alternative ways of referencing
61	61
62	62		##### By installing BGRABitmap package
63	63
64	64		Open bgrabitmappack.lpk as a package. Make sure it is possible to install it by going in the package window into "Options \> IDE Integration" and setting the package type to "designtime and runtime". Then in the package window, click on install. A dialog pops up, asking if the package must be added to Lazarus and if it needs to be compiled again. Choose Yes twice.
65	65
66	66		If everything is fine, Lazarus restarts and BGRABitmap units are available. If it does not work, you can simply add BGRABitmap to the search path without compiling Lazarus.
67	67
68	68		##### By adding BGRABitmap units to the search path
69	69
70	70		Another way is to add BGRABitmap units to the search path of the project. To do this, go to compiler options with menu Project \> Compiler options. In other unit files path, add the relative path to BGRABitmap. For example, if BGRABitmap is in a folder next to your project, the relative path could be "..\BGRABitmap".
71	71
72	72		If you copy BGRABitmap files in the same folder as your project, then you do not need to add such search path. However, it is not recommended because if you have multiple projects using the library, it could become a repetitive task to update to a new version of the library.
73	73
74	74		If you are lost with relative path, you can also add the relative path by adding the BGRABitmap unit to your project. To do so, open within your project the file bgrabitmap.pas. Then use menu Project \> Add file to project. Lazarus will ask if you want to add the file and the new directory to the project.
75	75
76	76		### Add some drawing
77	77
78	78		Add a painting event. To do this, click on the form, then go to the object inspector, in the event tab, and double click on the OnPaint line. Lazarus will add automatically a FormPaint handler to the main form unit. Add for example the following code inside it:
79	79
80	80		``` pascal
81	81		procedure TForm1.FormPaint(Sender: TObject);
82	82		var bmp: TBGRABitmap;
83	83		begin
84	84		bmp := TBGRABitmap.Create(ClientWidth, ClientHeight, BGRABlack);
85	85		bmp.FillRect(20, 20, 100, 40, BGRA(255,192,0), dmSet); //fill an orange rectangle
86	86		bmp.Draw(Canvas, 0, 0, True); //render BGRABitmap on the form
87	87		bmp.Free; //free memory
88	88		end;
89	89		```
90	90
91	91		As you can see, you need to define a [[TBGRABitmap class\|TBGRABitmap]] variable and create it. There are several constructors for [[TBGRABitmap class\|TBGRABitmap]]. The one used here creates a bitmap of size ClientWidth x ClientHeight and filled with black. ClientWidth and ClientHeight are form properties that return the available space for drawing inside the form.
92	92
93	93		The FillRect procedure takes usual parameters for drawing a rectangle, that is the upper-left corner followed by the lower-right corner plus 1. It means that the pixel at (100,40) is excluded from the rectangle.
94	94
95	95		After that, there is a color parameter with red/green/blue components, and a drawing mode. dmSet means to simply replace the pixels.
96	96
97	97		Do not forget to free the object after using it, to avoid a memory leak.
98	98
99	99		### Resulting code
100	100
101	101		You should obtain the following code:
102	102
103	103		``` pascal
104	104		unit UMain;
105	105
106	106		{$mode objfpc}{$H+}
107	107
108	108		interface
109	109
110	110		uses
111	111		Classes, SysUtils, FileUtil, LResources,
112	112		Forms, Controls, Graphics, Dialogs,
113	113		BGRABitmap, BGRABitmapTypes;
114	114
115	115		type
116	116
117	117		{ TForm1 }
118	118
119	119		TForm1 = class(TForm)
120	120		procedure FormPaint(Sender: TObject);
121	121		private
122	122		{ private declarations }
123	123		public
124	124		{ public declarations }
125	125		end;
126	126
127	127		var
128	128		Form1: TForm1;
129	129
130	130		implementation
131	131
132	132		{ TForm1 }
133	133
134	134		procedure TForm1.FormPaint(Sender: TObject);
135	135		var bmp: TBGRABitmap;
136	136		begin
137	137		bmp := TBGRABitmap.Create(ClientWidth, ClientHeight, BGRABlack);
138	138		bmp.FillRect(20, 20, 100, 40, BGRA(255, 192, 0), dmSet);
139	139		bmp.Draw(Canvas, 0, 0, True);
140	140		bmp.Free;
141	141		end;
142	142
143	143		initialization
144	144		{$I UMain.lrs}
145	145
146	146		end.
147	147		```
148	148
149	149		### Run the program
150	150
151	151		You should obtain a window filled in black with an orange rectangle in it.
152	152
153		-	~~<figure>~~
154		-	~~<img src="BGRATutorial1.png" title="BGRATutorial1.png" />~~
155		-	~~<figcaption>BGRATutorial1.png</figcaption>~~
156		-	~~</figure>~~
	153	+	![](/wiki-images/e/ea/BGRATutorial1.png)
157	154
158	155		[[BGRABitmap tutorial 2\|Go to next tutorial (image loading)]]
159	156
160	157		---
161	158		From the Free Pascal wiki, page "BGRABitmap tutorial 1", as it stood on 2020-02-11 after a change by Andry, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).
162	159		Category: BGRABitmap
163	160		Category: Graphics

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