OpenCV imencode pgm不编码正确的格式

我试图编码一个Mat CV_32FC1图像通过互联网发送它与base64，该过程工作，但OpenCV编码格式错误。示例：

I am trying to encode a Mat CV_32FC1 image to send it over the internet with base64, the process works but the OpenCV encodes in the wrong format. Example:

vector<unsigned char> buffer;
vector<int> compression_params;
compression_params.push_back(CV_IMWRITE_PXM_BINARY);
compression_params.push_back(0);
cv::imencode(".pgm", desc, buffer, compression_params);
printf("%s", &buffer[0]);

这将生成以下输出：

P2
64 15
255
0   0   0   0   1   0   0   0   0   1   0   0   0   0   0   0   1   0   0   0   0   0     0   0   0   0   
etc..

根据压缩参数和第一个参数不应该编码为二进制格式，它应该是ASCII。 （来源）

According to the compression parameter and the first parameter (P2) it shouldn't be encoded as a binary format, it should be ASCII. (Source)

本身不是一个问题，但是当我把 compression_params.push_back（0）更改为 compression_params.push_back（1） I得到此输出（无图像数据）：

In itself this isn't a problem, but when I change compression_params.push_back(0) to compression_params.push_back(1) I get this output (without image data):

P5
64 15
255

我在iOS上使用OpenCV 2.4.4，我如何解决这个问题，或者如何发送Mat的好方法不会丢失数据？

I am using OpenCV 2.4.4 on iOS, how can I fix this or alternatively how can I send a Mat the good way without losing data?