什么是c。使用OpenCV的imde code将其读取BLOB SQLite和德$ C $二值图像的最佳方式? [英] What is the best way to read binary image from blob SQLite and decode it using OpenCV imdecode?
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问题描述
我存储和C ++从SQLite数据库读取的图像文件,存储工作正常,但我失败了读取和转换字节OpenCV的CV ::使用imde code垫。这里是我的code:
I'm storing and reading image files from SQLite database in C++, the storing is working fine, but I have failed reading and converting the bytes to OpenCV cv::Mat using imdecode. Here is my code:
std::vector<cv::Mat> images;
std::vector<string> names;
std::vector<int> ids;
sqlite3 *db;
if (sqlite3_open("fr.db", &db) != SQLITE_OK)
{
printf("Open database failed\n");
return 0;
}
sqlite3_stmt *statement;
const char* sql = "SELECT * FROM Friends";
if (sqlite3_prepare_v2(db, sql, strlen(sql), &statement, 0) != SQLITE_OK)
{
printf("Open database failed\n");
return 0;
}
int result = 0;
while (true)
{
result = sqlite3_step(statement);
if (result == SQLITE_ROW)
{
int id = sqlite3_column_int(statement, 0);
ids.push_back(id);
int size = sqlite3_column_bytes(statement, 1);
std::vector<byte> data((byte)sqlite3_column_blob(statement, 1), size);
images.push_back(cv::imdecode(data, CV_LOAD_IMAGE_COLOR));
char* name = (char*)sqlite3_column_text(statement, 2);
names.push_back(name);
}
else
{
break;
}
}
问题是,imde code不建CV ::垫,但它返回空单..
先谢谢了。
The problem is that the imdecode does not build the cv::Mat but it returns empty one .. Thanks in advance.
推荐答案
现在的问题是在这条线:
The problem is in this line:
std::vector<byte> data((byte)sqlite3_column_blob(statement, 1), size);
在这里你是不是构建矢量
正常。
您应该使用的范围构造的:
template <class InputIterator>
vector (InputIterator first, InputIterator last,
const allocator_type& alloc = allocator_type());
和您的code会那么:
and your code will be then:
// Get the size of the vector
int size = sqlite3_column_bytes(statement, 1);
// Get the pointer to data
uchar* p = (uchar*)sqlite3_column_blob(statement,1);
// Initialize the vector with the data
vector<uchar> data(p, p+size);
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