用C語言進行BMP文件的讀寫

bmp是BitMap(位圖)的簡稱，也是所有windows上圖片顯示的基礎。所有的圖片格式，都必須轉換成bmp才能進行最終的顯示。所以，bmp文件的讀寫，就變得非常重要了。然而，很多人是借助於MFC類,C# 庫函數，OpenCV,OpenGL等庫函數進行bmp文件的讀寫。試想一下，如果你要在諸如DSP、FPGA之類的嵌入式設備上進行bmp文件的讀寫，總不能去安裝一個龐大的MFC,C#類庫吧？其實，我們完全可以拋開這些龐雜繁瑣的類庫和API函數，僅僅利用C語言，編寫幾個函數，就完全可以實現bmp文件的讀寫了。本文的意圖正在於此。

一個完整的bmp位圖文件，可以分為文件信息頭，位圖信息頭和RGB顏色陣列三個部分。文件信息頭主要包含“是否是BMP文件”，文件的大小等信息。而位圖信息頭則主要包含bmp文件的位圖寬度，高度，位平面，通道數等信息。而RGB顏色陣列，裡面才真正包含我們所需要的bmp位圖的像素數據。需要提醒的是，bmp位圖的顏色陣列部分，像素數據的存儲是以左下角為原點。也就是說，當你打開一個bmp圖片並顯示在電腦屏幕上的時，實際在存儲的時候，這個圖片的最左下角的像素是首先被存儲在bmp文件中的。之後，按照從左到右，從下到上的順序,依次進行像素數據的存儲。如果，你存儲的是3通道的位圖數據（也就是我們通常說的彩圖），那麼它是按照B0G0R0B1G1R1B2G2R2...的順序進行存儲的，同時，還要考慮到4字節對齊的問題。OK,了解了這些基本概念，相信，自己編程實現一些bmp文件的讀寫函數並非難事。這裡，我給出C語言的版本，僅供參考，如有錯誤，歡迎指正。

1. chenLeeCV.h
2. #ifndef CHENLEECV_H
3. #define CHENLEECV_H
5. typedef struct
6. {
7. //unsigned short bfType;
8. unsigned long bfSize;
9. unsigned short bfReserved1;
10. unsigned short bfReserved2;
11. unsigned long bfOffBits;
12. } ClBitMapFileHeader;
14. typedef struct
15. {
16. unsigned long biSize;
17. long biWidth;
18. long biHeight;
19. unsigned short biPlanes;
20. unsigned short biBitCount;
21. unsigned long biCompression;
22. unsigned long biSizeImage;
23. long biXPelsPerMeter;
24. long biYPelsPerMeter;
25. unsigned long biClrUsed;
26. unsigned long biClrImportant;
27. } ClBitMapInfoHeader;
29. typedef struct
30. {
31. unsigned char rgbBlue; //該顏色的藍色分量
32. unsigned char rgbGreen; //該顏色的綠色分量
33. unsigned char rgbRed; //該顏色的紅色分量
34. unsigned char rgbReserved; //保留值
35. } ClRgbQuad;
37. typedef struct
38. {
39. int width;
40. int height;
41. int channels;
42. unsigned char* imageData;
43. }ClImage;
45. ClImage* clLoadImage(char* path);
46. bool clSaveImage(char* path, ClImage* bmpImg);
48. #endif
50. chenLeeCV.cpp
51. #include "chenLeeCV.h"
52. #include <stdio.h>
53. #include <stdlib.h>
55. ClImage* clLoadImage(char* path)
56. {
57. ClImage* bmpImg;
58. FILE* pFile;
59. unsigned short fileType;
60. ClBitMapFileHeader bmpFileHeader;
61. ClBitMapInfoHeader bmpInfoHeader;
62. int channels = 1;
63. int width = 0;
64. int height = 0;
65. int step = 0;
66. int offset = 0;
67. unsigned char pixVal;
68. ClRgbQuad* quad;
69. int i, j, k;
71. bmpImg = (ClImage*)malloc(sizeof(ClImage));
72. pFile = fopen(path, "rb");
73. if (!pFile)
74. {
75. free(bmpImg);
76. return NULL;
77. }
79. fread(&fileType, sizeof(unsigned short), 1, pFile);
80. if (fileType == 0x4D42)
81. {
82. //printf("bmp file! \n");
84. fread(&bmpFileHeader, sizeof(ClBitMapFileHeader), 1, pFile);
85. /*printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
86. printf("bmp文件頭信息：\n");
87. printf("文件大小：%d \n", bmpFileHeader.bfSize);
88. printf("保留字：%d \n", bmpFileHeader.bfReserved1);
89. printf("保留字：%d \n", bmpFileHeader.bfReserved2);
90. printf("位圖數據偏移字節數：%d \n", bmpFileHeader.bfOffBits);*/
92. fread(&bmpInfoHeader, sizeof(ClBitMapInfoHeader), 1, pFile);
93. /*printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
94. printf("bmp文件信息頭\n");
95. printf("結構體長度：%d \n", bmpInfoHeader.biSize);
96. printf("位圖寬度：%d \n", bmpInfoHeader.biWidth);
97. printf("位圖高度：%d \n", bmpInfoHeader.biHeight);
98. printf("位圖平面數：%d \n", bmpInfoHeader.biPlanes);
99. printf("顏色位數：%d \n", bmpInfoHeader.biBitCount);
100. printf("壓縮方式：%d \n", bmpInfoHeader.biCompression);
101. printf("實際位圖數據占用的字節數：%d \n", bmpInfoHeader.biSizeImage);
102. printf("X方向分辨率：%d \n", bmpInfoHeader.biXPelsPerMeter);
103. printf("Y方向分辨率：%d \n", bmpInfoHeader.biYPelsPerMeter);
104. printf("使用的顏色數：%d \n", bmpInfoHeader.biClrUsed);
105. printf("重要顏色數：%d \n", bmpInfoHeader.biClrImportant);
106. printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");*/
108. if (bmpInfoHeader.biBitCount == 8)
109. {
110. //printf("該文件有調色板，即該位圖為非真彩色\n\n");
111. channels = 1;
112. width = bmpInfoHeader.biWidth;
113. height = bmpInfoHeader.biHeight;
114. offset = (channels*width)%4;
115. if (offset != 0)
116. {
117. offset = 4 - offset;
118. }
119. //bmpImg->mat = kzCreateMat(height, width, 1, 0);
120. bmpImg->width = width;
121. bmpImg->height = height;
122. bmpImg->channels = 1;
123. bmpImg->imageData = (unsigned char*)malloc(sizeof(unsigned char)*width*height);
124. step = channels*width;
126. quad = (ClRgbQuad*)malloc(sizeof(ClRgbQuad)*256);
127. fread(quad, sizeof(ClRgbQuad), 256, pFile);
128. free(quad);
130. for (i=0; i<height; i++)
131. {
132. for (j=0; j<width; j++)
133. {
134. fread(&pixVal, sizeof(unsigned char), 1, pFile);
135. bmpImg->imageData[(height-1-i)*step+j] = pixVal;
136. }
137. if (offset != 0)
138. {
139. for (j=0; j<offset; j++)
140. {
141. fread(&pixVal, sizeof(unsigned char), 1, pFile);
142. }
143. }
144. }
145. }
146. else if (bmpInfoHeader.biBitCount == 24)
147. {
148. //printf("該位圖為位真彩色\n\n");
149. channels = 3;
150. width = bmpInfoHeader.biWidth;
151. height = bmpInfoHeader.biHeight;
153. bmpImg->width = width;
154. bmpImg->height = height;
155. bmpImg->channels = 3;
156. bmpImg->imageData = (unsigned char*)malloc(sizeof(unsigned char)*width*3*height);
157. step = channels*width;
159. offset = (channels*width)%4;
160. if (offset != 0)
161. {
162. offset = 4 - offset;
163. }
165. for (i=0; i<height; i++)
166. {
167. for (j=0; j<width; j++)
168. {
169. for (k=0; k<3; k++)
170. {
171. fread(&pixVal, sizeof(unsigned char), 1, pFile);
172. bmpImg->imageData[(height-1-i)*step+j*3+k] = pixVal;
173. }
174. //kzSetMat(bmpImg->mat, height-1-i, j, kzScalar(pixVal[0], pixVal[1], pixVal[2]));
175. }
176. if (offset != 0)
177. {
178. for (j=0; j<offset; j++)
179. {
180. fread(&pixVal, sizeof(unsigned char), 1, pFile);
181. }
182. }
183. }
184. }
185. }
187. return bmpImg;
188. }
190. bool clSaveImage(char* path, ClImage* bmpImg)
191. {
192. FILE *pFile;
193. unsigned short fileType;
194. ClBitMapFileHeader bmpFileHeader;
195. ClBitMapInfoHeader bmpInfoHeader;
196. int step;
197. int offset;
198. unsigned char pixVal = '\0';
199. int i, j;
200. ClRgbQuad* quad;
202. pFile = fopen(path, "wb");
203. if (!pFile)
204. {
205. return false;
206. }
208. fileType = 0x4D42;
209. fwrite(&fileType, sizeof(unsigned short), 1, pFile);
211. if (bmpImg->channels == 3)//24位，通道，彩圖
212. {
213. step = bmpImg->channels*bmpImg->width;
214. offset = step%4;
215. if (offset != 4)
216. {
217. step += 4-offset;
218. }
220. bmpFileHeader.bfSize = bmpImg->height*step + 54;
221. bmpFileHeader.bfReserved1 = 0;
222. bmpFileHeader.bfReserved2 = 0;
223. bmpFileHeader.bfOffBits = 54;
224. fwrite(&bmpFileHeader, sizeof(ClBitMapFileHeader), 1, pFile);
226. bmpInfoHeader.biSize = 40;
227. bmpInfoHeader.biWidth = bmpImg->width;
228. bmpInfoHeader.biHeight = bmpImg->height;
229. bmpInfoHeader.biPlanes = 1;
230. bmpInfoHeader.biBitCount = 24;
231. bmpInfoHeader.biCompression = 0;
232. bmpInfoHeader.biSizeImage = bmpImg->height*step;
233. bmpInfoHeader.biXPelsPerMeter = 0;
234. bmpInfoHeader.biYPelsPerMeter = 0;
235. bmpInfoHeader.biClrUsed = 0;
236. bmpInfoHeader.biClrImportant = 0;
237. fwrite(&bmpInfoHeader, sizeof(ClBitMapInfoHeader), 1, pFile);
239. for (i=bmpImg->height-1; i>-1; i--)
240. {
241. for (j=0; j<bmpImg->width; j++)
242. {
243. pixVal = bmpImg->imageData[i*bmpImg->width*3+j*3];
244. fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
245. pixVal = bmpImg->imageData[i*bmpImg->width*3+j*3+1];
246. fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
247. pixVal = bmpImg->imageData[i*bmpImg->width*3+j*3+2];
248. fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
249. }
250. if (offset!=0)
251. {
252. for (j=0; j<offset; j++)
253. {
254. pixVal = 0;
255. fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
256. }
257. }
258. }
259. }
260. else if (bmpImg->channels == 1)//8位，單通道，灰度圖
261. {
262. step = bmpImg->width;
263. offset = step%4;
264. if (offset != 4)
265. {
266. step += 4-offset;
267. }
269. bmpFileHeader.bfSize = 54 + 256*4 + bmpImg->width;
270. bmpFileHeader.bfReserved1 = 0;
271. bmpFileHeader.bfReserved2 = 0;
272. bmpFileHeader.bfOffBits = 54 + 256*4;
273. fwrite(&bmpFileHeader, sizeof(ClBitMapFileHeader), 1, pFile);
275. bmpInfoHeader.biSize = 40;
276. bmpInfoHeader.biWidth = bmpImg->width;
277. bmpInfoHeader.biHeight = bmpImg->height;
278. bmpInfoHeader.biPlanes = 1;
279. bmpInfoHeader.biBitCount = 8;
280. bmpInfoHeader.biCompression = 0;
281. bmpInfoHeader.biSizeImage = bmpImg->height*step;
282. bmpInfoHeader.biXPelsPerMeter = 0;
283. bmpInfoHeader.biYPelsPerMeter = 0;
284. bmpInfoHeader.biClrUsed = 256;
285. bmpInfoHeader.biClrImportant = 256;
286. fwrite(&bmpInfoHeader, sizeof(ClBitMapInfoHeader), 1, pFile);
288. quad = (ClRgbQuad*)malloc(sizeof(ClRgbQuad)*256);
289. for (i=0; i<256; i++)
290. {
291. quad[i].rgbBlue = i;
292. quad[i].rgbGreen = i;
293. quad[i].rgbRed = i;
294. quad[i].rgbReserved = 0;
295. }
296. fwrite(quad, sizeof(ClRgbQuad), 256, pFile);
297. free(quad);
299. for (i=bmpImg->height-1; i>-1; i--)
300. {
301. for (j=0; j<bmpImg->width; j++)
302. {
303. pixVal = bmpImg->imageData[i*bmpImg->width+j];
304. fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
305. }
306. if (offset!=0)
307. {
308. for (j=0; j<offset; j++)
309. {
310. pixVal = 0;
311. fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
312. }
313. }
314. }
315. }
316. fclose(pFile);
318. return true;
319. }
321. Main.cpp
322. #include "stdafx.h"
323. #include "chenLeeCV.h"
326. int _tmain(int argc, _TCHAR* argv[])
327. {
328. ClImage* img = clLoadImage("c:/test.bmp");
329. bool flag = clSaveImage("c:/result.bmp", img);
330. if(flag)
331. {
332. printf("save ok... \n");
333. }
336. while(1);
337. return 0;
338. }