讀取和編寫BMP圖像

Question

我想加載和寫入BMP圖像，我只是嘗試加載字節並將其寫回到文件中，我的代碼如下：

unsigned char* readBMP(char* filename)
{
    int i;
    FILE* f = fopen(filename, "rb");
    unsigned char info[54];
    fread(info, sizeof(unsigned char), 54, f); // read the 54-byte header

    // extract image height and width from header
    int width = *(int*)&info[18];
    int height = *(int*)&info[22];

    int size = 3 * width * height;
    unsigned char* data = new unsigned char[size]; // allocate 3 bytes per pixel
    fread(data, sizeof(unsigned char), size, f); // read the rest of the data at once
    fclose(f);

    ofstream fout;
    fout.open("konik2.bmp", ios::binary | ios::out);
    fout.write((char*) &info, sizeof(info));
    fout.write((char*) &data, sizeof(data));

    fout.close();
    return data;
}

但是輸出文件已損壞，請使用hexeditor打開它，我看到有完全不同的字節。 我所做的就是先讀取metaData，然后讀取圖像本身的數據，為什么它不起作用？ 我忽略了什么嗎？ 感謝幫助！

Answer 1

 fout.write((char*)&data, sizeof(data)); 

您要寫入的data不是&data 。 並使用size代替sizeof(data) （只有4或8）

應該填充size ，以便“以字節為單位的寬度”是4的倍數。

您要檢查位圖文件（ bpp ）的位計數，以確保它適用於任何位圖。

unsigned char* readBMP(char* filename)
{
    FILE* f = fopen(filename, "rb");
    unsigned char info[54];
    fread(info, sizeof(unsigned char), 54, f); // read the 54-byte header

    // extract image height and width from header
    int width = *(int*)&info[18];
    int height = *(int*)&info[22];
    int bpp = *(int*)&info[28];

    int size = ((width * bpp + 31) / 32) * 4 * height; //<==== change
    unsigned char* data = new unsigned char[size]; 
    fread(data, sizeof(unsigned char), size, f); 
    fclose(f);

    ofstream fout;
    fout.open("c:\\test\\_out.bmp", ios::binary);
    fout.write((char*)&info, sizeof(info));
    fout.write((char*)data, size); //<==== change

    fout.close();
    return data;
}