RGBQUAD
时间: 2024-02-18 14:59:23 浏览: 31
RGBQUAD是Windows编程中用来表示颜色的结构体,它包含了一个像素点的红、绿、蓝三个颜色分量和一个保留字节,分别用一个字节来存储。在DIB中,一个像素点的颜色通常使用RGBQUAD结构体来表示。RGBQUAD结构体的定义如下:
```
typedef struct tagRGBQUAD {
BYTE rgbBlue;
BYTE rgbGreen;
BYTE rgbRed;
BYTE rgbReserved;
} RGBQUAD;
```
其中,rgbBlue、rgbGreen和rgbRed分别表示蓝、绿、红三个颜色分量,取值范围都是0~255;rgbReserved是保留字节,用于对齐结构体,通常是0。
相关问题
nFileSize -= sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER); nFileSize -= 256 * sizeof(RGBQUAD);
这段代码的作用是计算文件大小减去位图文件头和位图信息头的大小,再减去256个RGBQUAD结构体的大小。
1. `nFileSize -= sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);` 这行代码计算了位图文件头和位图信息头的大小,并将其从文件大小中减去。位图文件头(BITMAPFILEHEADER)和位图信息头(BITMAPINFOHEADER)是位图文件的前两个部分,用于描述位图的属性和结构。
2. `nFileSize -= 256 * sizeof(RGBQUAD);` 这行代码计算了256个RGBQUAD结构体的总大小,并将其从文件大小中减去。RGBQUAD结构体用于表示位图中每个像素的颜色信息,每个RGBQUAD结构体占用4个字节。
通过这两行代码的计算,可以得到去除位图文件头、位图信息头和256个RGBQUAD结构体后的文件大小。
void Zoom(const char *filename,double lx,double ly){ FILE *fp = fopen(filename,"rb"); if (fp == NULL) printf("Error"); BITMAPFILEHEADER fileHead; fread(&fileHead, sizeof(BITMAPFILEHEADER), 1, fp); BITMAPINFOHEADER infoHead; fread(&infoHead, sizeof(BITMAPINFOHEADER), 1, fp); int width = infoHead.biWidth; int height = infoHead.biHeight; int biCount = infoHead.biBitCount; RGBQUAD *pColorTable; int pColorTableSize = 0; pColorTable = new RGBQUAD[256]; fread(pColorTable, sizeof(RGBQUAD), 256, fp); pColorTableSize = 1024; unsigned char *pBmpBuf; int lineByte = (width*biCount / 8 + 3) / 4 * 4; pBmpBuf = new unsigned char[lineByte*height]; fread(pBmpBuf, lineByte*height, 1, fp); fclose(fp); int dstWidth = round(double(lx*width)); int dstHeight = round(double(ly*height)); int lineByte2 = (dstWidth*biCount / 8 + 3) / 4 * 4; unsigned char*pBmpBuf2; pBmpBuf2 = new unsigned char[lineByte2*dstHeight]; for (int i = 0; i < dstHeight; ++i){ for (int j = 0; j < dstWidth; ++j){ unsigned char *p; p = (unsigned char *)(pBmpBuf2 + lineByte2*i + j); (*p) = 255; } } int x = 0; int y = 0; for (int i = 0; i < height; ++i){ for (int j = 0; j < width; ++j){ unsigned char *p1, *p2; x = round(double(lx*j)); y = round(double(ly*i)); p1 = (unsigned char *)(pBmpBuf + i*lineByte + j); p2 = (unsigned char *)(pBmpBuf2 + y*lineByte2 + x); (*p2) = (*p1); } }
这段代码是一个图像缩放的函数,下面是对代码的中文注释:
```cpp
// 将指定文件中的图像进行缩放后保存
// 参数filename为图像文件名,lx和ly为横向和纵向的缩放比例
void Zoom(const char *filename, double lx, double ly){
FILE *fp = fopen(filename,"rb");
if (fp == NULL)
printf("Error");
// 读取位图文件头和位图信息头
BITMAPFILEHEADER fileHead;
fread(&fileHead, sizeof(BITMAPFILEHEADER), 1, fp);
BITMAPINFOHEADER infoHead;
fread(&infoHead, sizeof(BITMAPINFOHEADER), 1, fp);
// 获取图像的宽度、高度和颜色位数
int width = infoHead.biWidth;
int height = infoHead.biHeight;
int biCount = infoHead.biBitCount;
RGBQUAD *pColorTable;
int pColorTableSize = 0;
// 读取调色板数据
pColorTable = new RGBQUAD[256];
fread(pColorTable, sizeof(RGBQUAD), 256, fp);
pColorTableSize = 1024;
// 读取图像数据
unsigned char *pBmpBuf;
int lineByte = (width * biCount / 8 + 3) / 4 * 4;
pBmpBuf = new unsigned char[lineByte * height];
fread(pBmpBuf, lineByte * height, 1, fp);
fclose(fp);
// 计算缩放后的图像宽度和高度,并计算缩放后的每行字节数
int dstWidth = round(double(lx * width));
int dstHeight = round(double(ly * height));
int lineByte2 = (dstWidth * biCount / 8 + 3) / 4 * 4;
// 创建缩放后的图像数据缓冲区,并初始化为白色
unsigned char *pBmpBuf2;
pBmpBuf2 = new unsigned char[lineByte2 * dstHeight];
for (int i = 0; i < dstHeight; ++i){
for (int j = 0; j < dstWidth; ++j){
unsigned char *p;
p = (unsigned char *)(pBmpBuf2 + lineByte2 * i + j);
(*p) = 255;
}
}
// 对每个像素进行缩放处理
int x = 0;
int y = 0;
for (int i = 0; i < height; ++i){
for (int j = 0; j < width; ++j){
unsigned char *p1, *p2;
x = round(double(lx * j));
y = round(double(ly * i));
p1 = (unsigned char *)(pBmpBuf + i * lineByte + j);
p2 = (unsigned char *)(pBmpBuf2 + y * lineByte2 + x);
(*p2) = (*p1);
}
}
// 将缩放后的图像数据保存到新文件中
FILE *fp2 = fopen("zoomed.bmp", "wb");
if (fp2 == NULL)
printf("Error");
fwrite(&fileHead, sizeof(BITMAPFILEHEADER), 1, fp2);
fwrite(&infoHead, sizeof(BITMAPINFOHEADER), 1, fp2);
fwrite(pColorTable, sizeof(RGBQUAD), 256, fp2);
fwrite(pBmpBuf2, lineByte2 * dstHeight, 1, fp2);
fclose(fp2);
// 释放内存
delete[] pColorTable;
delete[] pBmpBuf;
delete[] pBmpBuf2;
}
```
希望这些注释能帮助你理解代码的功能和实现过程。如果还有其他问题,请随时提问。