How do I convert the image into ASCII format?

Convert jpg image in ppm P3 ASCII format using Opencv

• Using opencv imwrite function I managed to convert jpg image in ppm P6 format. Mat image = imread(picPath); vector<int> compression_params; compression_params.push_back(CV_IMWRITE_PXM_BINARY); compression_params.push_back(1); imwrite("bez.ppm", image, compression_params); Problem is that I actually have to convert jpg image in ppm P3 ASCII format. Does anyone know how to do it? Thanks! EDIT: In the project I have the following piece of code where I check the maximum value of pixels: int maxVal; fscanf(in, "%d", &maxVal); if (maxVal != 255) { printf("Input file error: Not a Netpbm color image with 256 levels\n"); exit(0); } When I set parameter 0 then I get: Not a Netpbm color image with 256 levels! When I do the conversion from jpg to ppm p3 with irfanview program works.

• Answer:

  The code involved is in the file modules/imgcodecs/src/grfmt_pxm.cpp in the OpenCV source tree. It sets the internal flag isBinary like this according to the compression parameters: for( size_t i = 0; i < params.size(); i += 2 ) if( params[i] == CV_IMWRITE_PXM_BINARY ) isBinary = params[i+1] != 0; so, if you want ASCII (P3) you need to have compression_params.push_back(0) and have image type CV_8UC1, CV_8UC3 or CV_16UC1.