c++ - BMP Exporter 不工作 C++

Question

因此，正如标题所述，我在使用 C++ 导出 .bmp(24 位 bmp)时遇到了问题。我正在做一个学校项目类型的事情，我需要一些帮助。为了了解 .BMP 的工作原理，我查看了维基百科页面，并从 here 获得了一些帮助。 ，但我还是想不通。这是我所拥有的:

//Export the map as a .bmp
void PixelMap::exportMap(const char* fileName)
{
    //Size of the file in bytes
    int fileSize = 54 + (3 * width * height);

    //The sections of the file
    unsigned char generalHeader[14] = {'B','M',0,0, 0,0,0,0, 0,0,54,0, 0,0};
    unsigned char DIBHeader[40]     = {40,0,0,0, 0,0,0,0, 0,0,0,0, 1,0,24,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0};
    unsigned char pixelArray[]      = "";

    //Set the binary portion of the generalHeader, mainly just file size
    generalHeader[2] = (unsigned char)(fileSize);
    generalHeader[3] = (unsigned char)(fileSize << 8);
    generalHeader[4] = (unsigned char)(fileSize << 16);
    generalHeader[5] = (unsigned char)(fileSize << 24);

    //The binary variable portion of the DIB header
    DIBHeader[4]  = (unsigned char)(width);
    DIBHeader[5]  = (unsigned char)(width << 8);
    DIBHeader[6]  = (unsigned char)(width << 16);
    DIBHeader[7]  = (unsigned char)(width << 24);
    DIBHeader[8]  = (unsigned char)(height);
    DIBHeader[9]  = (unsigned char)(height << 8);
    DIBHeader[10] = (unsigned char)(height << 16);
    DIBHeader[11] = (unsigned char)(height << 24);
    int picSize = 3 * width * height;
    DIBHeader[20] = (unsigned char)(picSize);
    DIBHeader[21] = (unsigned char)(picSize << 8);
    DIBHeader[22] = (unsigned char)(picSize << 16);
    DIBHeader[23] = (unsigned char)(picSize << 24);

    //Loop through all width and height places to add all pixels
    int counter = 0;
    for(short j = height; j >= 0; j--)
    {
        for(short i = 0; i < width; i++)
        {
            //Add all 3 RGB values
            pixelArray[counter] = pixelColour[i, j].red;
            counter++;
            pixelArray[counter] = pixelColour[i, j].green;
            counter++;
            pixelArray[counter] = pixelColour[i, j].blue;
            counter++;
        }
    }

    //Open it
    ofstream fileWorking(fileName);

    //Write the sections
    fileWorking << generalHeader;
    fileWorking << DIBHeader;
    fileWorking << pixelArray;

    //NO MEMORY LEAKS 4 ME
    fileWorking.close();
}

这是名为“PixelMap”的类的一部分，基本上是帧缓冲区或表面。 PixelMap 具有变量“宽度”、“高度”和结构数组“pixelColour”。 (包含 3 个字符的结构称为“红色”、“绿色”和“蓝色”)如果您想查看该类，请看这里。 (这只是一个骨架，试图先把.bmp弄下来)

//This is a pixel map, mainly for exporting BMPs
class PixelMap
{
public:

    //The standard pixel variables
    int width;
    int height;
    Colour pixelColour[];

    //The constructor will set said variables
    PixelMap(int Width, int Height);

    //Manipulate pixels
    void setPixel(int X, int Y, char r, char g, char b);

    //Export the map
    void exportMap(const char* fileName);
};

(颜色是结构体)

所以我的问题是，当我尝试运行它时，我得到了这个: 所以 pixelArray，要导出的颜色数组被破坏了。我认为这与未正确指定大小有关，但我尝试为其分配正确的值(3 * 宽度 * 高度(3 是 RGB))，但它说它需要是一个常量值。

非常感谢对此问题的任何帮助!

Answer 1

代替

unsigned char pixelArray[]      = "";

你可以使用:

std::vector<unsigned char> pixelArray(3*width*height,0);

这声明了一个包含 3*width*height 元素的 vector ，初始化为 0。您可以使用与数组版本相同的语法访问元素(除了，如注释中指出的，您必须注意将二进制值正确写入输出文件)。