位圖點處理

Question

會喜歡我的任務之一集思廣益一些幫助。我將編寫一個程序來處理.bmp圖像的基本點處理。程序將打開.bmp文件進行讀取和寫入，並不會改變頭部的任何部位，但根據命令行參數文件中的像素值：

-fromrow x, where x specifies the bottommost row to process 
-torowx, where x specifies the topmost row to process 
-fromcol x, where x specifies the leftmost column to process 
-tocol x, where x specifies the rightmost column to process 
-op x, where x is one of the following: 
    - 1 = threshold the image (any pixel value in the specifies range over 127 is changed to 255, and pixel values 127 or less is changed to 0) 
    - 2 = negative (any pixel value p in the specified range is changed to 255-p) 

To process image data, you will need to make use of the following: 
- each pixel value is an unsigned char 
- the number of rows in the image is stored as an int at position (byte address) 22 in the file 
- the number of columns in the image is stored as an int at position (byte address) 18 in the file 
- the position at which the pixel data starts is an int stored at position (byte address) 10 in the file 
- pixel information is stored row by row, starting from the bottommost row in the image (row 0) and progressing upwards. within a row; pixel information is stored left to right. padding is added to the end of each row to make row length a multiple of 4 bytes (if the row has 479 columns, there is one extra padding at the end of the row before the next row starts) 

我有點失落至於如何開始，但我想我應該做一個結構位圖首先像這樣？

struct bitmap { 
    unsigned int startrow; 
    unsigned int endrow; 
    unsigned int startcol; 
    unsigned int endcol; 
} 

任何人都可以幫助我通過什麼，我需要做的字節地址，該任務引用？任何其他頭腦風暴的建議也將不勝感激。謝謝！

Answer 1

可以通過在二進制模式打開文件讀取的原始字節：

FILE *fid = fopen("blah.bmp", "rb"); 

然後可以讀出的數據的一定量的這樣的：

int num_actually_read = fread(p, sizeof(*p), num_to_read, fid); 

其中p是一個指向一些緩衝。在這種情況下，你可能想p是uint8_t *類型的，因爲你所面對的大多是原始字節。

或者，你可以在這樣一個文件跳來跳去：

fseek(fid, pos, SEEK_SET); 

我希望這是足以讓你去。

Answer 2

您需要一個指針指向文件的字節地址22和18。一旦指向這些地址，您將需要取消引用指針以獲取行和列值。然後你必須將你的指針指向地址10，然後逐個遍歷像素。