[英]Read bitmap file into structure
我想將位圖文件讀入一個結構體並像這樣操作它。 制作鏡像效果,但我無法理解應該創建哪種結構才能讀取它。
謝謝您的幫助。
»這是您手動加載 .BMP 文件的方式
位圖文件格式:
繼續代碼部分。 這是我們需要創建的結構來保存位圖文件頭。
#pragma pack(push, 1)
typedef struct tagBITMAPFILEHEADER
{
WORD bfType; //specifies the file type
DWORD bfSize; //specifies the size in bytes of the bitmap file
WORD bfReserved1; //reserved; must be 0
WORD bfReserved2; //reserved; must be 0
DWORD bfOffBits; //specifies the offset in bytes from the bitmapfileheader to the bitmap bits
}BITMAPFILEHEADER;
#pragma pack(pop)
bftype字段會檢查您是否確實在加載 .BMP 文件,如果是,則該字段應為 0x4D42。
現在我們需要創建我們的bitmapinfoheader結構。 這包含有關我們位圖的信息。
#pragma pack(push, 1)
typedef struct tagBITMAPINFOHEADER
{
DWORD biSize; //specifies the number of bytes required by the struct
LONG biWidth; //specifies width in pixels
LONG biHeight; //specifies height in pixels
WORD biPlanes; //specifies the number of color planes, must be 1
WORD biBitCount; //specifies the number of bits per pixel
DWORD biCompression; //specifies the type of compression
DWORD biSizeImage; //size of image in bytes
LONG biXPelsPerMeter; //number of pixels per meter in x axis
LONG biYPelsPerMeter; //number of pixels per meter in y axis
DWORD biClrUsed; //number of colors used by the bitmap
DWORD biClrImportant; //number of colors that are important
}BITMAPINFOHEADER;
#pragma pack(pop)
現在開始加載我們的位圖。
unsigned char *LoadBitmapFile(char *filename, BITMAPINFOHEADER *bitmapInfoHeader)
{
FILE *filePtr; //our file pointer
BITMAPFILEHEADER bitmapFileHeader; //our bitmap file header
unsigned char *bitmapImage; //store image data
int imageIdx=0; //image index counter
unsigned char tempRGB; //our swap variable
//open file in read binary mode
filePtr = fopen(filename,"rb");
if (filePtr == NULL)
return NULL;
//read the bitmap file header
fread(&bitmapFileHeader, sizeof(BITMAPFILEHEADER),1,filePtr);
//verify that this is a .BMP file by checking bitmap id
if (bitmapFileHeader.bfType !=0x4D42)
{
fclose(filePtr);
return NULL;
}
//read the bitmap info header
fread(bitmapInfoHeader, sizeof(BITMAPINFOHEADER),1,filePtr);
//move file pointer to the beginning of bitmap data
fseek(filePtr, bitmapFileHeader.bfOffBits, SEEK_SET);
//allocate enough memory for the bitmap image data
bitmapImage = (unsigned char*)malloc(bitmapInfoHeader->biSizeImage);
//verify memory allocation
if (!bitmapImage)
{
free(bitmapImage);
fclose(filePtr);
return NULL;
}
//read in the bitmap image data
fread(bitmapImage,bitmapInfoHeader->biSizeImage,1,filePtr);
//make sure bitmap image data was read
if (bitmapImage == NULL)
{
fclose(filePtr);
return NULL;
}
//swap the R and B values to get RGB (bitmap is BGR)
for (imageIdx = 0;imageIdx < bitmapInfoHeader->biSizeImage;imageIdx+=3)
{
tempRGB = bitmapImage[imageIdx];
bitmapImage[imageIdx] = bitmapImage[imageIdx + 2];
bitmapImage[imageIdx + 2] = tempRGB;
}
//close file and return bitmap image data
fclose(filePtr);
return bitmapImage;
}
現在要利用所有這些:
BITMAPINFOHEADER bitmapInfoHeader;
unsigned char *bitmapData;
// ...
bitmapData = LoadBitmapFile("mypic.bmp",&bitmapInfoHeader);
//now do what you want with it, later on I will show you how to display it in a normal window
稍后我將提供寫入 .BMP,以及如何加載 targa 文件以及如何顯示它們。«
引自: http ://www.vbforums.com/showthread.php?261522-CC-Loading-Bitmap-Files-%28Manually%29(用戶:BeholderOf)。 (做了一些小修正)
這里是一個簡短的工作示例。
它將 wav 文件轉換為 bmp(很久以前我玩得很開心)。
代碼:
#include <stdio.h>
#include <strings.h>
#include <sndfile.h>
#include <stdlib.h>
#include <math.h>
#define RATE 44100
typedef struct {
unsigned short type; /* Magic identifier */
unsigned int size; /* File size in bytes */
unsigned int reserved;
unsigned int offset; /* Offset to image data, bytes */
} HEADER;
typedef struct {
unsigned int size; /* Header size in bytes */
int width,height; /* Width and height of image */
unsigned short planes; /* Number of colour planes */
unsigned short bits; /* Bits per pixel */
unsigned int compression; /* Compression type */
unsigned int imagesize; /* Image size in bytes */
int xresolution,yresolution; /* Pixels per meter */
unsigned int ncolours; /* Number of colours */
unsigned int importantcolours; /* Important colours */
} INFOHEADER;
typedef struct {
unsigned char r,g,b,junk;
} COLOURINDEX;
int main(int argc, char *argv[]){
int i,j,rd;
int gotindex = 0;
unsigned char grey,r,g,b;
double ampl;
short _2byte[2];
HEADER header;
INFOHEADER infoheader;
COLOURINDEX colourindex[256];
FILE *fptr;
SNDFILE* sndfile = NULL;
SF_INFO sfinfo;
long rate = RATE;
void (*bmpread)();
void _eightbit(){
if(fread(&grey, sizeof(unsigned char), 1, fptr) != 1){
fprintf(stderr,"Image read failed\n");
exit(-1);
}
if (gotindex){
ampl = colourindex[grey].r * 64. +
colourindex[grey].g * 128.+
colourindex[grey].b * 64.;
} else {
ampl = grey * 256. - 32768.;
}
// printf("%.2f\n", ampl);
}
void _twentyfourbit(){
do{
if((rd = fread(&b, sizeof(unsigned char), 1, fptr)) != 1) break;
if((rd = fread(&g, sizeof(unsigned char), 1, fptr)) != 1) break;
if((rd = fread(&r, sizeof(unsigned char), 1, fptr)) != 1) break;
}while(0);
if(rd != 1){
fprintf(stderr,"Image read failed\n");
exit(-1);
}
ampl = r * 64. + g * 128. + b * 64. - 32768.;
// printf("%.2f\n", ampl);
}
if (argc < 3){
printf("Usage: %s <input.bmp> <output.wav> [samplerate]\n", argv[0]);
printf("For example:\n\t%s pict.bmp sample.wav 44100 2\n", argv[0]);
exit(0);
}
printf("Input file: %s\n", argv[1]);
printf("Output file: %s\n", argv[2]);
if(argc > 3) rate = atoi(argv[3]);
if(rate < 4000) rate = 4000;
//if(argc > 4) channels = atoi(argv[4]);
sfinfo.samplerate = rate;
sfinfo.channels = 2;
sfinfo.format = SF_FORMAT_WAV|SF_FORMAT_PCM_16;
if((fptr = fopen(argv[1],"r")) == NULL) {
fprintf(stderr,"Unable to open BMP file \"%s\"\n",argv[1]);
exit(-1);
}
/* Read and check BMP header */
if(fread(&header.type, 2, 1, fptr) != 1){
fprintf(stderr, "Failed to read BMP header\n");
exit(-1);
}
if(header.type != 'M'*256+'B'){
fprintf(stderr, "File is not bmp type\n");
exit(-1);
}
do{
if((rd = fread(&header.size, 4, 1, fptr)) != 1) break;
printf("File size: %d bytes\n", header.size);
if((rd = fread(&header.reserved, 4, 1, fptr)) != 1) break;
if((rd = fread(&header.offset, 4, 1, fptr)) != 1) break;
printf("Offset to image data is %d bytes\n", header.offset);
}while(0);
if(rd =! 1){
fprintf(stderr, "Error reading file\n");
exit(-1);
}
/* Read and check the information header */
if (fread(&infoheader, sizeof(INFOHEADER), 1, fptr) != 1) {
fprintf(stderr,"Failed to read BMP info header\n");
exit(-1);
}
printf("Image size = %d x %d\n", infoheader.width, infoheader.height);
printf("Number of colour planes is %d\n", infoheader.planes);
printf("Bits per pixel is %d\n", infoheader.bits);
printf("Compression type is %d\n", infoheader.compression);
printf("Number of colours is %d\n", infoheader.ncolours);
printf("Number of required colours is %d\n", infoheader.importantcolours);
/* Read the lookup table if there is one */
for (i=0; i<255; i++){
colourindex[i].r = rand() % 256;
colourindex[i].g = rand() % 256;
colourindex[i].b = rand() % 256;
colourindex[i].junk = rand() % 256;
}
if (infoheader.ncolours > 0) {
for (i=0; i<infoheader.ncolours; i++){
do{
if ((rd = fread(&colourindex[i].b, sizeof(unsigned char),1,fptr)) != 1)
break;
if ((rd = fread(&colourindex[i].g, sizeof(unsigned char),1,fptr)) != 1)
break;
if ((rd = fread(&colourindex[i].r, sizeof(unsigned char),1,fptr)) != 1)
break;
if ((rd = fread(&colourindex[i].junk, sizeof(unsigned char),1,fptr)) != 1)
break;
}while(0);
if(rd != 1){
fprintf(stderr,"Image read failed\n");
exit(-1);
}
printf("%3d\t%3d\t%3d\t%3d\n", i,
colourindex[i].r, colourindex[i].g, colourindex[i].b);
}
gotindex = 1;
}
if(infoheader.bits < 8){
printf("Too small image map depth (%d < 8)\n", infoheader.bits);
exit(-1);
}
/* Seek to the start of the image data */
fseek(fptr, header.offset, SEEK_SET);
printf("Creating 16bit WAV %liHz.\n", rate);
sndfile = sf_open(argv[2], SFM_WRITE, &sfinfo);
if(sndfile == NULL){
fprintf(stderr, "Cannot open output file!\n"); exit(-1);
}
bmpread = _eightbit;
if(infoheader.bits == 24)
bmpread = _twentyfourbit;
/* Read the image */
for (j=0;j<infoheader.height;j++) {
_2byte[1] = 32700;
for (i=0;i<infoheader.width;i++) {
bmpread();
_2byte[0] = (short)ampl;
sf_write_short(sndfile, _2byte, 2);
_2byte[1] = 0;
} // i
} // j
fclose(fptr);
sf_close(sndfile);
}
因此,要讀取位圖,您需要@ollo 回答的結構,但也有一種更簡單的方法。
#include <wingdi.h>
訪問所有結構,而無需將它們寫入單獨的文件中。在 CS50x 課程中,但問題是生成的 output.bmp 在CS50 ide上完全正確,但在裝有Windows 10 的本地計算機上不起作用。 所以我對它做了一些改變,它奏效了。 該代碼對於 Linux 和其他操作系統也是可移植的。我在其中進行了更改並將在您的系統上運行的代碼在這里
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