Convert Binary Data to OpenCV Image Format

在影像處理時，常常會讀取影像資料(binary data)後轉成影像格式(cv::Mat)，在進行影像操作。

那我們如何轉成可用的OpenCV影像格式呢?

首先讀取檔案後得到binary data，在進行解碼轉成cv::Mat。

當然如果單純讀檔後轉成OpenCV影像格式，OpenCV是有提供cv::imread這個API可以使用。

這裡會詳細解釋是有機會透過Web傳送影像或者存取資料庫時會用到。

編碼格式Decode Format：

• Windows bitmaps - *.bmp, *.dib (always supported)
• JPEG files - *.jpeg, *.jpg, *.jpe (see the Notes section)
• JPEG 2000 files - *.jp2 (see the Notes section)
• Portable Network Graphics - *.png (see the Notes section)
• Portable image format - *.pbm, *.pgm, *.ppm (always supported)
• Sun rasters - *.sr, *.ras (always supported)
• TIFF files - *.tiff, *.tif (see the Notes section)

OpenCV編碼參數：

• CV_LOAD_IMAGE_COLOR = Color
• CV_LOAD_IMAGE_GRAYSCALE = Gray Level
• CV_LOAD_IMAGE_ANYCOLOR = Source Color。
• CV_LOAD_IMAGE_ANYDEPTH = return 16-bit/32-bit image

C API

CvMat* buf = cvCreateMat(1, nBinaryDataLength, CV_8UC1);
buf->data.ptr = (unsigned char *)sBinaryData;
if(buf->data.ptr == NULL){
    cvReleaseMat(&buf);
    return NULL;
}
IplImage* image = cvDecodeImage(buf, CV_LOAD_IMAGE_ANYCOLOR);
cvReleaseMat(&buf);

C++ API

std::vector< char > data(sBinaryData, nBinaryDataLength);
cv::Mat image = cv::imdecode( cv::Mat(data), CV_LOAD_IMAGE_ANYCOLOR );
data~vector();

更多OpenCV文章請參考：OpenCV Tutorial (學習筆記)