c++ - Resizing the image in C# and sending it to OpenCV results in distorted image -


this follow-up question related this one.
basically, have dll uses opencv image manipulation.
there 2 methods, 1 accepting image-path, , other 1 accepting cv::mat.
1 working image-path works fine.
1 accepts image problematic.

here method accepts filename(dll): 

cdll2_api void classify(const char * img_path, char* out_result, int* length_of_out_result, int n) {     auto classifier = reinterpret_cast<classifier*>(gethandle());      cv::mat img = cv::imread(img_path);     cv::imshow("img recieved c#", img);     std::vector<predictionresults> result = classifier->classify(std::string(img_path), n);     std::string str_info = "";     //...     *length_of_out_result = ss.str().length(); }

here method accepts image(dll) : 

cdll2_api void classify_image(unsigned char* img_pointer, unsigned int height, unsigned int width,                                int step, char* out_result, int* length_of_out_result, int top_n_results)     {         auto classifier = reinterpret_cast<classifier*>(gethandle());         cv::mat img = cv::mat(height, width, cv_8uc3, (void*)img_pointer, step);         std::vector<prediction> result = classifier->classify(img, top_n_results);          //...         *length_of_out_result = ss.str().length();     }

here code in c# application : dll import: 

[dllimport(@"cdll2.dll", callingconvention = callingconvention.cdecl, charset = charset.ansi)]         static extern void classify_image(intptr img, uint height, uint width, int step, byte[] out_result, out int out_result_length, int top_n_results = 2);

the method sends image dll : 

private string classify_usingimage(bitmap img, int top_n_results) {     byte[] res = new byte[200];     int len;     bitmapdata bmpdata;     bmpdata = img.lockbits(new rectangle(0, 0, img.width, img.height), imagelockmode.readonly, img.pixelformat);     classify_image(bmpdata.scan0, (uint)bmpdata.height, (uint)bmpdata.width, bmpdata.stride, res, out len, top_n_results);     //remember unlock!!!     img.unlockbits(bmpdata);      string s = asciiencoding.ascii.getstring(res);     return s; }

now, works when send image dll. if use imshow() show received image, image shown fine.

the actual problem :

however, when resize same image , send using same method above, image distorted.

i need add that, if resize image using given c# method below, save it, , pass filename dll opened using classify(std::string(img_path), n); works perfectly.

here screenshot showing example of happening:
image sent c# without being resized :

enter image description here
when same image first resized , sent dll:

enter image description here

here image first resized (in c#), saved disk , filepath sent dll: enter image description here

this snippet responsible resizing (c#): 

/// <summary> /// resize image specified width , height. /// </summary> /// <param name="image">the image resize.</param> /// <param name="width">the width resize to.</param> /// <param name="height">the height resize to.</param> /// <returns>the resized image.</returns> public static bitmap resizeimage(image image, int width, int height) {     var destrect = new rectangle(0, 0, width, height);     var destimage = new bitmap(width, height);      destimage.setresolution(image.horizontalresolution, image.verticalresolution);      using (var graphics = graphics.fromimage(destimage))     {         graphics.compositingmode = compositingmode.sourcecopy;         graphics.compositingquality = compositingquality.highquality;         graphics.interpolationmode = interpolationmode.highqualitybicubic;         graphics.smoothingmode = smoothingmode.highquality;         graphics.pixeloffsetmode = pixeloffsetmode.highquality;          using (var wrapmode = new imageattributes())         {             wrapmode.setwrapmode(wrapmode.tileflipxy);             graphics.drawimage(image, destrect, 0, 0, image.width, image.height, graphicsunit.pixel, wrapmode);         }     }      return destimage; }

and original image

this classify method uses filepath read images: 

std::vector<predictionresults> classifier::classify(const std::string & img_path, int n) {     cv::mat img = cv::imread(img_path);     cv::mat resizedimage;     std::vector<predictionresults> results;     std::vector<float> output;     // cv::imshow((std::string("img classify path") + type2str(img.type())), img);     if (isresizedenabled())     {         resizeimage(img, resizedimage);         output = predict(resizedimage);     }     else     {         output = predict(img);         img.release();     }      n = std::min<int>(labels_.size(), n);     std::vector<int> maxn = argmax(output, n);     (int = 0; < n; ++i)     {         int idx = maxn[i];         predictionresults r;         r.label = labels_[idx];         r.accuracy = output[idx];         results.push_back(r);     }      return results; }

and resizeimage used in method above : 

void classifier::resizeimage(const cv::mat & source_image, cv::mat& resizedimage) {     size size(getresizeheight(), getresizeheight());     cv::resize(source_image, resizedimage, size);//resize image      check(!resizedimage.empty()) << "unable decode image "; }

problem 2:
distortion after resizing aside, facing discrepancy between resizing in c# , resizing using opencv itself.
have created method using emgucv (also given below) , passed needed information , did not face such distortions happen when resize image in c# , send dll.
however, discrepancy made me want understand causing these issues.
here method uses emgucv.mat code works irrespective of resizing: 

private string classify_usingmat(string imgpath, int top_n_results) {     byte[] res = new byte[200];     int len;      emgu.cv.mat img = new emgu.cv.mat(imgpath, imreadmodes.color);      if (chkresizeimagecshap.checked)     {         cvinvoke.resize(img, img, new size(256, 256));     }      classify_image(img.datapointer, (uint)img.height, (uint)img.width, img.step, res, out len, top_n_results);      string s = asciiencoding.ascii.getstring(res);     return s; }

why care?
because, different accuracy when use opencv resize (both when use emgucv's cvinvoke.resize() , cv::resize()) resizing image in c#, saving disk , send image path opencv.
either need fix distortion happening when deal images in c#, or need understand why resizing in opencv has different results c# resizing.

so summarize issues , points made far :

  1. all situations intact, if resize image inside c# application, , pass info did before, image distorted (example given above)
  2. if resize image, save disk, , give filename opencv create new cv::mat, works without issues.
  3. if use emugcv , instead of working bitmap, use emug.cv.mat , send needed parameters using mat object c#, no distortion happens. however, accuracy resized image c#( see #2 ), different 1 resized image using opencv. doesn't make difference if resize image before hand using cvinvoke.resize() c#, , send resulting image dll, or send original image (using emgucv) , resizing in cpp code using cv::resize(). prevents me using emgucv or passing image original image , resizing inside dll using opencv.

here images different results, showing issues :

--------------------no resizing------------------------------ 1.using bitmap-no resize, =>safe, acc=580295 2.using emgu.mat-no resize =>safe, acc=0.580262 3.using filepath-no resize, =>safe, acc=0.580262 --------------------resize in c#------------------------------ 4.using bitmap-csharp resize, =>unsafe, acc=0.770425 5.using emgu.mat-emguresize, =>unsafe, acc=758335 6.**using filepath-csharp resize, =>unsafe, acc=0.977649** --------------------resize in dll------------------------------ 7.using bitmap-dll resize, =>unsafe, acc=0.757484 8.using emgu.dll resize, =>unsafe, acc=0.758335 9.using filepath-dll resize, =>unsafe, acc=0.758335

i need accuracy @ #6. can see emgucv resize , opencv resize function used in dll, act similar , don't work expected(i.e. #2)!, c# resize method applied on image problematic, while if resized, saved , filename passed, result fine.

you can see screen shots depicting different scenarios here : http://imgur.com/a/xbgiq

ok.thanks dear god , great helps @edchum, work.! did use imdecode @edchum suggested. how functions in dll , c# : 

#ifdef cdll2_exports #define cdll2_api __declspec(dllexport) #else #define cdll2_api __declspec(dllimport) #endif  #include "classification.h"  extern "c" {     cdll2_api void classify_image(unsigned char* img_pointer, long data_len, char* out_result, int* length_of_out_result, int top_n_results = 2); //... }

the actual method : 

cdll2_api void classify_image(unsigned char* img_pointer, long data_len,                               char* out_result, int* length_of_out_result, int top_n_results) {     auto classifier = reinterpret_cast<classifier*>(gethandle());     vector<unsigned char> inputimagebytes(img_pointer, img_pointer + data_len);     cv::mat img = imdecode(inputimagebytes, cv_load_image_color);      cv::imshow("img recieved c#", img);      std::vector<prediction> result = classifier->classify(img, top_n_results);     //...     *length_of_out_result = ss.str().length(); }

here c# dll import: 

[dllimport(@"cdll2.dll", callingconvention = callingconvention.cdecl, charset = charset.ansi)] static extern void classify_image(byte[] img, long data_len, byte[] out_result, out int out_result_length, int top_n_results = 2);

and actual method sending image dll: 

private string classify_usingimage(bitmap image, int top_n_results) {     byte[] result = new byte[200];     int len;     bitmap img;      if (chkresizeimagecshap.checked)         img = resizeimage(image, int.parse(txtwidth.text), (int.parse(txtheight.text)));     else         img = image;      //this situations, image not read disk, , stored in memort(e.g. image comes camera or snapshot)     imageformat fmt = new imageformat(image.rawformat.guid);     var imagecodecinfo = imagecodecinfo.getimageencoders().firstordefault(codec => codec.formatid == image.rawformat.guid);     if (imagecodecinfo == null)     {         fmt = imageformat.jpeg;     }      using (memorystream ms = new memorystream())     {         img.save(ms, fmt);         byte[] image_byte_array = ms.toarray();         classify_image(image_byte_array, ms.length, result, out len, top_n_results);     }      return asciiencoding.ascii.getstring(result); }

by doing after resizing image c#, dont face distortions @ all. couldnt however, figure out why resize on opencv part wouldnt work expected!


Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj...
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer ...
Read more

c# - Asp.net web api : redirect unauthorized requst to forbidden page -

im trying redirect unauthorized request forbidden page instead i'm getting forbidden page in response body , how can fix ? here's startup class : app.createperowincontext(storecontext.create); app.createperowincontext<applicationusermanager>(applicationusermanager.create); app.createperowincontext<applicationsigninmanager>(applicationsigninmanager.create); app.usecookieauthentication(new cookieauthenticationoptions { authenticationtype = defaultauthenticationtypes.applicationcookie, expiretimespan = timespan.fromdays(30), }); app.useexternalsignincookie(defaultauthenticationtypes.externalcookie); app.usetwofactorsignincookie(defaultauthenticationtypes.twofactorcookie, timespan.fromminutes(5)); app.usetwofactorrememberbrowsercookie(defaultauthenticationtypes.twofactorrememberbrowsercookie); the method im trying reach : [httpget] [authorize(roles = "admin")] public string getcurrentusername() { return userman...
Read more