我正在尝试使用 Qt QDataStream 读取 TGA 文件头。我从具有固定类型的规范中具有以下结构：
#pragma pack(push, 1)
/* TGA header */
struct tga_header_t
{
quint8 id_lenght; /* size of image id */
quint8 colormap_type; /* 1 is has a colormap */
quint8 image_type; /* compression type */
/* Color Map Specification */
quint16 cm_origin; /* colormap origin */
quint16 cm_length; /* colormap length */
quint8 cm_size; /* colormap size */
/* Image Specification */
quint16 x_origin; /* bottom left x coord origin */
quint16 y_origin; /* bottom left y coord origin */
quint16 width; /* picture width (in pixels) */
quint16 height; /* picture height (in pixels) */
quint8 pixel_depth; /* bits per pixel: 8, 16, 24 or 32 */
quint8 image_descriptor; /* 24 bits = 0x00; 32 bits = 0x80 */
};
#pragma pack(pop)
我用 QFile 打开一个文件，然后用它构造一个 QDataStream ：
QFile file(path);
tga_header_t header;
file.open(QIODevice::ReadOnly);
QDataStream stream(&file);
stream >> header.id_lenght >>
header.colormap_type >>
header.image_type >>
header.cm_origin >>
header.cm_length >>
header.cm_size >>
header.x_origin >>
header.y_origin >>
header.width >>
header.height >>
header.pixel_depth >>
header.image_descriptor;
qDebug() << header.id_lenght << "id_lenght" <<
header.colormap_type << "colormap_type" <<
header.image_type << "image_type" <<
header.cm_origin << "cm_origin" <<
header.cm_length << "cm_length" <<
header.cm_size << "cm_size" <<
header.x_origin << "x_origin" <<
header.y_origin << "y_origin" <<
header.width << "width" <<
header.height << "height" <<
header.pixel_depth << "pixel_depth" <<
header.image_descriptor << "image_descriptor" <<
"SIZE:" << sizeof(header);
问题在于我得到的宽度和高度：
0 id_lenght 0 colormap_type 2 image_type 0 cm_origin 0 cm_length 0 cm_size 0 x_origin 0 y_origin 22021 width 3 height 24 pixel_depth 0 image_descriptor SIZE: 18
我应该得到 1366 和 768。如果我 hexdump 我得到的文件：
0000000 0000 0002 0000 0000 0000 0000 0556 0300
0000010 0018 0000 0000 0000 0000 0000 0000 0000
这很奇怪，因为它在开始时有一个额外的字节，而在 和 之间的某个地方缺少另一个0x0002字节0x0556。
更新：
使用 fstream 有效，如果我错了，请纠正我，但我认为<<操作符不能像我预期的那样工作（只读取填充结构变量所需的大小）。
stream.read((char*)&header.id_lenght, sizeof(header.id_lenght));
stream.read((char*)&header.colormap_type, sizeof(header.colormap_type));
stream.read((char*)&header.image_type, sizeof(header.image_type));
stream.read((char*)&header.cm_origin, sizeof(header.cm_origin));
stream.read((char*)&header.cm_length, sizeof(header.cm_length));
stream.read((char*)&header.cm_size, sizeof(header.cm_size));
stream.read((char*)&header.x_origin, sizeof(header.x_origin));
stream.read((char*)&header.y_origin, sizeof(header.y_origin));
stream.read((char*)&header.width, sizeof(header.width));
stream.read((char*)&header.height, sizeof(header.height));
stream.read((char*)&header.pixel_depth, sizeof(header.pixel_depth));
stream.read((char*)&header.image_descriptor, sizeof(header.image_descriptor));
使用 QDataStream::readRawData 也可以：
stream.readRawData((char*)&header.id_lenght, sizeof(header.id_lenght));
stream.readRawData((char*)&header.colormap_type, sizeof(header.colormap_type));
stream.readRawData((char*)&header.image_type, sizeof(header.image_type));
stream.readRawData((char*)&header.cm_origin, sizeof(header.cm_origin));
stream.readRawData((char*)&header.cm_length, sizeof(header.cm_length));
stream.readRawData((char*)&header.cm_size, sizeof(header.cm_size));
stream.readRawData((char*)&header.x_origin, sizeof(header.x_origin));
stream.readRawData((char*)&header.y_origin, sizeof(header.y_origin));
stream.readRawData((char*)&header.width, sizeof(header.width));
stream.readRawData((char*)&header.height, sizeof(header.height));
stream.readRawData((char*)&header.pixel_depth, sizeof(header.pixel_depth));
stream.readRawData((char*)&header.image_descriptor, sizeof(header.image_descriptor));