如何解决调整bmp图片的大小
我正在尝试调整bmp图像的大小,并且几乎可以正常工作,但是由于某些原因,我得到了多余的字节,这些字节用零填充。有点用,但是我想知道这些零从何而来。
我不确定它是否以某种方式与那些零相关联,但是有时图像深度(biBitCount)从原始文件中的24更改为32。我无法弄清楚为什么这样做。不幸的是,我没有保存截图。
我敢肯定,我只是犯了一些看不见的愚蠢错误。请帮帮我。 original bmp double sized bmp with extra zeros
我的代码:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "bmp.h"
float atoi2_0(char* S);
int main(int argc,char *argv[])
{
// ensure proper usage
if (argc != 4)
{
fprintf(stderr,"Usage: ./resize f infile outfile\n");
return 1;
}
// remember filenames
float f = atoi2_0(argv[1]);
if(f == -1 || f <= 0.0 || f > 100)
{
printf("Usage: ./resize f infile outfile\n");
return 1;
}
char *infile = argv[2];
char *outfile = argv[3];
// open input file
FILE *inptr = fopen(infile,"r");
if (inptr == NULL)
{
fprintf(stderr,"Could not open %s.\n",infile);
return 2;
}
// open output file
FILE *outptr = fopen(outfile,"w");
if (outptr == NULL)
{
fclose(inptr);
fprintf(stderr,"Could not create %s.\n",outfile);
return 3;
}
// read infile's BITMAPFILEHEADER
BITMAPFILEHEADER bf;
fread(&bf,sizeof(BITMAPFILEHEADER),1,inptr);
// read infile's BITMAPINFOHEADER
BITMAPINFOHEADER bi;
fread(&bi,sizeof(BITMAPINFOHEADER),inptr);
// ensure infile is (likely) a 24-bit uncompressed BMP 4.0
if (bf.bfType != 0x4d42 || bf.bfOffBits != 54 || bi.biSize != 40 ||
bi.biBitCount != 24 || bi.biCompression != 0)
{
fclose(outptr);
fclose(inptr);
fprintf(stderr,"Unsupported file format.\n");
return 4;
}
int oldpadding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
bi.biWidth *= f;
bi.biHeight *= f;
int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
bi.biSizeImage = ((sizeof(RGBTRIPLE) * bi.biWidth) + padding) * abs(bi.biHeight);
bf.bfSize = bi.biSizeImage + 54;
// write outfile's BITMAPFILEHEADER
fwrite(&bf,outptr);
// write outfile's BITMAPINFOHEADER
fwrite(&bi,outptr);
float df = f - (int)f;
int revdf = 1 / df;
int bbw = bi.biWidth / f;
for (int i = 0,biHeight = abs(bi.biHeight); i < biHeight; i++)
{
RGBTRIPLE * oldtriple = (RGBTRIPLE*)calloc(bbw,sizeof(RGBTRIPLE));
if (oldtriple == NULL)
{
fclose(inptr);
fclose(outptr);
return 5;
}
fread(oldtriple,sizeof(RGBTRIPLE),bbw,inptr);
RGBTRIPLE * triple = (RGBTRIPLE*)calloc(bi.biWidth,sizeof(RGBTRIPLE));
if (triple == NULL)
{
free(oldtriple);
fclose(inptr);
fclose(outptr);
return 5;
}
for (int j = 0; j < bbw; j++)
{
int jxf = j * f;
for (int n = 0; n < f; n++)
{
*(triple + jxf + n) = *(oldtriple + j);
}
}
for (int j = 0; j < f; j++)
{
if (i % revdf && f - j == df) continue;
fwrite(triple,bi.biWidth,outptr);
for (int n = 0; n < padding; n++)
{
fputc(0x00,outptr);
}
}
fseek(inptr,oldpadding,SEEK_CUR);
free(triple);
free(oldtriple);
}
// close infile
fclose(inptr);
// close outfile
fclose(outptr);
// success
return 0;
}
float atoi2_0(char* S)//kinda atoi for floats
{
int strl = strlen(S);
for (int i = 0; i < strl; i++)//input check
{
if ((S[i] < '0' || S[i] > '9') && (S[i] != '.'))
{
printf("Invalid input");
return -1;
}
}
float a = atoi(S);
char D[10] = { 0 };
for (int i = 0; i < strl; i++)
{
if (S[i] == '.')
{
++i;
for (int j = 0; i < strl; i++,j++)
{
D[j] = S[i];
}
}
}
a += (float)atoi(D) / pow(10,strlen(D));
return a;
}
BMP.h :
``` // BMP-related data types based on Microsoft's own
#include <stdint.h>
// aliases for C/C++ primitive data types
// https://msdn.microsoft.com/en-us/library/cc230309.aspx
typedef uint8_t BYTE;
typedef uint32_t DWORD;
typedef int32_t LONG;
typedef uint16_t WORD;
// information about the type,size,and layout of a file
// https://msdn.microsoft.com/en-us/library/dd183374(v=vs.85).aspx
typedef struct
{
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} __attribute__((__packed__))
BITMAPFILEHEADER;
// information about the dimensions and color format
// https://msdn.microsoft.com/en-us/library/dd183376(v=vs.85).aspx
typedef struct
{
DWORD biSize;
LONG biWidth;
LONG biHeight;
WORD biPlanes;
WORD biBitCount;
DWORD biCompression;
DWORD biSizeImage;
LONG biXPelsPerMeter;
LONG biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} __attribute__((__packed__))
BITMAPINFOHEADER;
// relative intensities of red,green,and blue
// https://msdn.microsoft.com/en-us/library/dd162939(v=vs.85).aspx
typedef struct
{
BYTE rgbtBlue;
BYTE rgbtGreen;
BYTE rgbtRed;
} __attribute__((__packed__))
RGBTRIPLE;
解决方法
是的,我自己修复了。问题出在周期长度上。
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