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我在用 C++ 读取位图文件时遇到了麻烦。我的代码仅在行填充等于 3 个字节时才有效。任何其他填充都会产生奇怪的事情 - 有时我无法读取输出文件，有时我可以打开它，但它看起来像垃圾并且具有不同的宽度和高度。

这是我从位图文件中读取数据的函数：

void read_bmp(ImageFile* Image, const char* filename){
FILE* pFile;
unsigned char* buffer;
unsigned int bufferSize, offset_bitmapData, counter_PixelCounter=0, offset_paddingSum=0;

pFile = fopen(filename, "rb"); 
if(pFile==NULL) throw ERR_FILE_DOES_NOT_EXIST;

fseek(pFile, 0, SEEK_SET);
bufferSize = 54;
buffer = new unsigned char[bufferSize];
if(fread(buffer, sizeof(char), bufferSize, pFile)!=bufferSize) throw ERR_FILE_READING_ERROR;
if(readBytes_int(0, 2, buffer)!=0x4D42) throw ERR_NO_BMP_HEADER;

offset_bitmapData = readBytes_int(0x0A, 4, buffer);
Image->ImageWidth = readBytes_int(0x12, 4, buffer);
Image->ImageHeight = readBytes_int(0x16, 4, buffer);
Image->FileSize = readBytes_int(0x02, 4, buffer);
Image->bbpInfo = readBytes_int(0x1C, 2,buffer);
Image->Padding = (4 - (Image->ImageWidth*3)%4)%4;
cout<<"width "<<Image->ImageWidth<<endl;
cout<<"padding "<<(int)Image->Padding<<endl;

if(readBytes_int(0x0E, 4, buffer)!=40) throw ERR_NO_BITMAPINFOHEADER;

delete[] buffer;
bufferSize = Image->ImageWidth * Image->ImageHeight * 3 + Image->ImageHeight * Image->Padding;
buffer = new unsigned char[bufferSize];
if(buffer==NULL) throw ERR_BAD_ALLOC;
fseek(pFile, offset_bitmapData, SEEK_SET);

if(fread(buffer, sizeof(char), bufferSize, pFile)!=bufferSize) throw ERR_FILE_READING_ERROR;
fclose(pFile);

Image->PixelArray = new unsigned char**[Image->ImageHeight];
counter_PixelCounter = 0;

for(int height = Image->ImageHeight-1; height >= 0; height--)
{
    Image->PixelArray[height] = new unsigned char*[Image->ImageWidth];

    for(int width = 0; width < Image->ImageWidth; width++)
    {
        Image->PixelArray[height][width] = new unsigned char[3];

        Image->PixelArray[height][width][0] = (unsigned char)readBytes_int((counter_PixelCounter ) * 3  + offset_paddingSum + 2, 1, buffer);
        Image->PixelArray[height][width][1] = (unsigned char)readBytes_int((counter_PixelCounter ) * 3 + offset_paddingSum + 1, 1, buffer);
        Image->PixelArray[height][width][2] = (unsigned char)readBytes_int((counter_PixelCounter ) * 3 + offset_paddingSum, 1, buffer);

        counter_PixelCounter++;

    } 
    offset_paddingSum += Image->Padding;
}
cout<<counter_PixelCounter<<endl;
cout<<"File loaded successfully\n";
}
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2 回答 2

4

文件说

DIB 由两个不同的部分组成：描述位图尺寸和颜色的 BITMAPINFO 结构，以及定义位图像素的字节数组。数组中的位被打包在一起，但每条扫描线必须用零填充以在 LONG 数据类型边界上结束。

您的代码错误地实现了粗体子句。您正在四舍五入像素数，而不是字节数。

于 2013-04-07T14:05:54.577 回答
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.BMP 文件中有四个字节用于描述文件地址 0x22 中填充的大小。

您可以阅读它并跳过填充。另请参阅此问题和回复： C++: .bmp to byte array in a file

于 2013-10-25T07:59:31.647 回答