无法正确读取.bmp头文件(Trouble reading .bmp header file properly)
我试图接受一个.bmp文件并最终逐个编辑像素，但我想出了INFOHEADER结构中返回给我的宽度和高度的问题。 返回的宽度是13107200，高度是65536.但是，每当我运行程序时，总共只计算了60003个像素。 我不知道为什么会这样。 任何帮助将不胜感激。
#include <stdio.h> #include <stdlib.h> int main( int argc, char *argv[] ){ //define structures typedef struct { unsigned short int Type; /* Magic identifier */ unsigned int Size; /* File size in bytes */ unsigned short int Reserved1, Reserved2; unsigned int Offset; /* Offset to data (in B)*/ }HEADER; /* -- 14 Bytes -- */ typedef struct { unsigned int Size; /* Header size in bytes */ int Width, Height; /* Width / Height of image */ unsigned short int Planes; /* Number of colour planes */ unsigned short int Bits; /* Bits per pixel */ unsigned int Compression; /* Compression type */ unsigned int ImageSize; /* Image size in bytes */ int xResolution, yResolution;/* Pixels per meter */ unsigned int Colors; /* Number of colors */ unsigned int ImportantColors;/* Important colors */ }INFOHEADER; /* -- 40 Bytes -- */ typedef struct { unsigned char Red, Green, Blue; }PIXEL; //make instance of all three structures HEADER data; INFOHEADER data2; PIXEL pixel; //declare file read pointer FILE *file; //declare fileout read pointer //FILE *fileout; //declare file printed file pointer // open file 1 of argument counter and return 0 apon error if( !(file = fopen( "CU.bmp","rb")))return 0; //read HEADER data into data fread(&data,sizeof(HEADER),1,file); //read IB+NFOHEADER data into data2 fread(&data2,sizeof(INFOHEADER),1,file); //Print PIXEL data //Allocate space for pixelarray PIXEL **pixelarray; int r=0,c=0,rows=data2.Height,collumns=data2.Width; pixelarray= malloc(rows*sizeof(PIXEL *)); for(r=0; r<rows; r++){ pixelarray[r]=malloc(collumns*sizeof(PIXEL)); } //fill pixel array with pixel structs r=0;c=0; int pixelnum=1; while( fread(&pixel,sizeof(PIXEL),1,file) ){ if(c == collumns){ c=0; r++; } pixelarray[r][c] = pixel; printf("\nPixel %10d: %02X%02X%02X",pixelnum,pixelarray[r][c].Red,pixelarray[r][c].Blue,pixelarray[r][c].Green); fflush(stdout); c++;pixelnum++; } free(pixelarray); fclose(file); //close the files prior to exitingI am trying to take in a .bmp file and eventually edit the pixels one by one but I am coming up with a problem with the width and height returned to me in the INFOHEADER struct. The width returned is 13107200 and the height is 65536. However, whenever I run through the program a total of only 60003 total pixels are counted. I have no idea why this is. Any help would be greatly appreciated.
#include <stdio.h> #include <stdlib.h> int main( int argc, char *argv[] ){ //define structures typedef struct { unsigned short int Type; /* Magic identifier */ unsigned int Size; /* File size in bytes */ unsigned short int Reserved1, Reserved2; unsigned int Offset; /* Offset to data (in B)*/ }HEADER; /* -- 14 Bytes -- */ typedef struct { unsigned int Size; /* Header size in bytes */ int Width, Height; /* Width / Height of image */ unsigned short int Planes; /* Number of colour planes */ unsigned short int Bits; /* Bits per pixel */ unsigned int Compression; /* Compression type */ unsigned int ImageSize; /* Image size in bytes */ int xResolution, yResolution;/* Pixels per meter */ unsigned int Colors; /* Number of colors */ unsigned int ImportantColors;/* Important colors */ }INFOHEADER; /* -- 40 Bytes -- */ typedef struct { unsigned char Red, Green, Blue; }PIXEL; //make instance of all three structures HEADER data; INFOHEADER data2; PIXEL pixel; //declare file read pointer FILE *file; //declare fileout read pointer //FILE *fileout; //declare file printed file pointer // open file 1 of argument counter and return 0 apon error if( !(file = fopen( "CU.bmp","rb")))return 0; //read HEADER data into data fread(&data,sizeof(HEADER),1,file); //read IB+NFOHEADER data into data2 fread(&data2,sizeof(INFOHEADER),1,file); //Print PIXEL data //Allocate space for pixelarray PIXEL **pixelarray; int r=0,c=0,rows=data2.Height,collumns=data2.Width; pixelarray= malloc(rows*sizeof(PIXEL *)); for(r=0; r<rows; r++){ pixelarray[r]=malloc(collumns*sizeof(PIXEL)); } //fill pixel array with pixel structs r=0;c=0; int pixelnum=1; while( fread(&pixel,sizeof(PIXEL),1,file) ){ if(c == collumns){ c=0; r++; } pixelarray[r][c] = pixel; printf("\nPixel %10d: %02X%02X%02X",pixelnum,pixelarray[r][c].Red,pixelarray[r][c].Blue,pixelarray[r][c].Green); fflush(stdout); c++;pixelnum++; } free(pixelarray); fclose(file); //close the files prior to exiting最满意答案
我想你的问题是structure alignment 。 你可以在这里和这里参考它。 要消除它，请使用#pragma指令。 所以你的结构声明将是这样的：
#pragma pack(push) // push current alignment to stack #pragma pack(1) // set alignment to 1 byte boundary typedef struct { unsigned short int Type; /* Magic identifier */ unsigned int Size; /* File size in bytes */ unsigned short int Reserved1; unsigned short int Reserved2; unsigned int Offset; /* Offset to data (in B)*/ }HEADER; /* -- 14 Bytes -- */ typedef struct { unsigned int Size; /* Header size in bytes */ int Width; int Height; /* Width / Height of image */ unsigned short int Planes; /* Number of colour planes */ unsigned short int Bits; /* Bits per pixel */ unsigned int Compression; /* Compression type */ unsigned int ImageSize; /* Image size in bytes */ int xResolution; int yResolution;/* Pixels per meter */ unsigned int Colors; /* Number of colors */ unsigned int ImportantColors;/* Important colors */ }INFOHEADER; /* -- 40 Bytes -- */ typedef struct { unsigned char Red; unsigned char Green; unsigned char Blue; }PIXEL; #pragma pack(pop) // restore original alignment from stack这可以正确读取BMP图像的宽度和高度。 在读取图像数据时，请直接进行：
for( r=0; r<rows; r++ ) { for( c=0; c<collumns; c++ ) // read pixel data from image { fread(&pixelarray[r][c] , 1, sizeof(PIXEL), file); pixelnum++; } }I guess your problem is structure alignment. You can refer to it here and here. To eliminate it use the #pragma directive. So your structure declaration would be something like this:
#pragma pack(push) // push current alignment to stack #pragma pack(1) // set alignment to 1 byte boundary typedef struct { unsigned short int Type; /* Magic identifier */ unsigned int Size; /* File size in bytes */ unsigned short int Reserved1; unsigned short int Reserved2; unsigned int Offset; /* Offset to data (in B)*/ }HEADER; /* -- 14 Bytes -- */ typedef struct { unsigned int Size; /* Header size in bytes */ int Width; int Height; /* Width / Height of image */ unsigned short int Planes; /* Number of colour planes */ unsigned short int Bits; /* Bits per pixel */ unsigned int Compression; /* Compression type */ unsigned int ImageSize; /* Image size in bytes */ int xResolution; int yResolution;/* Pixels per meter */ unsigned int Colors; /* Number of colors */ unsigned int ImportantColors;/* Important colors */ }INFOHEADER; /* -- 40 Bytes -- */ typedef struct { unsigned char Red; unsigned char Green; unsigned char Blue; }PIXEL; #pragma pack(pop) // restore original alignment from stackThis correctly reads the width and height of BMP image. Further while reading image data, do it directly:
for( r=0; r<rows; r++ ) { for( c=0; c<collumns; c++ ) // read pixel data from image { fread(&pixelarray[r][c] , 1, sizeof(PIXEL), file); pixelnum++; } }更多推荐
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