Question

如何用c++编程实现提取给定图像中任意一点的RGB颜色值

Answer 1

控制台 读取BMP图片文件 输出指定点的颜色分量

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>

typedef unsigned long DWORD;
typedef int BOOL;
typedef unsigned char BYTE;
typedef unsigned short WORD;

typedef struct tagBITMAPINFOHEADER{
DWORD biSize;
long biWidth;
long biHeight;
WORD biPlanes;
WORD biBitCount;
DWORD biCompression;
DWORD biSizeImage;
long biXPelsPerMeter;
long biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} BITMAPINFOHEADER;

int ReadBmp(const char* szFileName);
int GetDIBColor(int X, int Y, BYTE *r, BYTE *g, BYTE *b);

BITMAPINFOHEADER bih;
BYTE *Buffer = NULL;
long LineByteWidth;

int main(void)
{
int x, y;
BYTE r, g, b;
int n;
char szfilename[255] = "c:\\1.bmp";

if (ReadBmp(szfilename) == 0)
{
printf("failure to read file %s", szfilename);
return 1;
}

printf("Width: %ld\n", bih.biWidth);
printf("Height: %ld\n", bih.biHeight);
printf("BitCount: %d\n\n", (int)bih.biBitCount);

while(1)
{
printf("input the X:");
scanf("%d", &x);
if (x < 0)
break;
printf("input the Y:");
scanf("%d", &y);

if (GetDIBColor(x, y, &r, &g, &b) == 1)
printf("(%d, %d): r:%d, g:%d, b:%d\n", x, y, (int)r, (int)g, (int)b);
else
printf("input error.\n");
}

free(Buffer);
return 0;
}

int ReadBmp(const char* szFileName)
{
FILE *file;
WORD bfh[7];
long dpixeladd;

if (NULL == (file = fopen(szFileName, "rb")))
{
return 0;
}
printf("%s\n", szFileName);

fread(&bfh, sizeof(WORD), 7, file);
if (bfh[0] != (WORD)(((WORD)'B')|('M'<<8)))
{
fclose(file);
return 0;
}

fread(&bih, sizeof(BITMAPINFOHEADER), 1, file);

if (bih.biBitCount < 24)
{
fclose(file);
return 0;
}

dpixeladd = bih.biBitCount / 8;
LineByteWidth = bih.biWidth * (dpixeladd);
if ((LineByteWidth % 4) != 0)
LineByteWidth += 4 - (LineByteWidth % 4);

if ((Buffer = (BYTE*)malloc(sizeof(BYTE)* LineByteWidth * bih.biHeight)) != NULL)
{
fread(Buffer, LineByteWidth * bih.biHeight, 1, file);

fclose(file);
return 1;
}

fclose(file);
return 0;
}

int GetDIBColor(int X, int Y, BYTE *r, BYTE *g, BYTE *b)
{
int dpixeladd;
BYTE *ptr;
if (X < 0 || X >= bih.biWidth || Y < 0 || Y >= bih.biHeight)
{
return 0;
}

dpixeladd = bih.biBitCount / 8;
ptr = Buffer + X * dpixeladd + (bih.biHeight - 1 - Y) * LineByteWidth;

*b = *ptr;
*g = *(ptr + 1);
*r = *(ptr + 2);

return 1;
}