Introduction
A recent stab at grabbing images from the Flea2 camera using APIs from the FlyCapture2 SDK by Point Gray Research (PGR). Additionally, the camera was to be used in “Format 7 mode”, so that we may grab partial regions of the complete image.
This application builds on the AsynchTriggerEx C++ example provided by PGR, so that the user can grab images from the camera either by way of software triggers, or from an external hardware triggers.
Using Format7 mode to grab partial images
The Format7ImageSettings data structure is modified in order to set the desired output image size, pixel formats etc. Standard FlyCapture API calls are used to perform all necessary camera actions: connect to camera, disconnect from camera, start image capturing, retrieve image buffers etc. When the using the default equipment setup, the input images obtained are grayscales of 24 x 480 pixels consisting of an array of dark gray spots against a lighter shade of gray background.
Converting FlyCapture images into OpenCV images
In the image grabbing loop, FlyCapture2-obtained images are converted into OpenCV-compatible images by copying the pixel data from one to the other:
1 2 3 | memcpy( img->imageData, image.GetData(), data_size ); |
Thresholding the grayscale image into binary (black & white)
The OpenCV grayscale image is then thresholded to produce a black and white (binary) image, from which we can use for things like detecting the number and location of the spots. Depending on the equipment used and lighting arrangement, some experimentation is probably needed to come up with an optimal threshold value.
1 2 3 4 5 | cvThreshold( img, // source_img, img_bw, // destination image 140, // threhold val. 255, // max. val CV_THRESH_BINARY ); // binary type ); |
Original FlyCapture grayscale image, set to a Format 7 partial image (24 x 480 pixels) and converted to OpenCV format:
Thresholded to a black and white (binary) image:
Full code listing:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 | // CameraTest.cpp : Defines entry point for console application.#include "stdafx.h"#include "FlyCapture2.h"#include <cv.h>#include <highgui.h> // Disable C4996 warnings#pragma warning(disable: 4996)#define SOFTWARE_TRIGGER_CAMERAusing namespace FlyCapture2;const int col_size = 24;const int row_size = 480;const int data_size = row_size * col_size;// Forward declarationsbool CheckSoftwareTriggerPresence( Camera* pCam );bool PollForTriggerReady( Camera* pCam );bool FireSoftwareTrigger( Camera* pCam );void PrintError( Error error );void ReleaseImage( IplImage* pimg, IplImage* pimg_bw, CvMemStorage* pstorage );void GrabImages( Camera* pcam, IplImage* pimg, IplImage* pimg_bw, CvMemStorage* pstorage, int cnt );// Main Control Loopint _tmain(int argc, _TCHAR* argv[]){ Camera cam; CameraInfo camInfo; Error error; BusManager busMgr; PGRGuid guid; Format7PacketInfo fmt7PacketInfo; Format7ImageSettings fmt7ImageSettings; CvMemStorage* storage = NULL; IplImage* img = NULL; IplImage* img_bw = NULL; TriggerMode triggerMode; // Create OpenCV structs for grayscale image img = cvCreateImage( cvSize( col_size, row_size ), IPL_DEPTH_8U, 1 ); img_bw = cvCloneImage( img ); storage = cvCreateMemStorage( 0 ); // Get Flea2 camera error = busMgr.GetCameraFromIndex( 0, &guid ); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } // Connect to the camera error = cam.Connect( &guid ); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } // Get camera information error = cam.GetCameraInfo(&camInfo); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; }#ifndef SOFTWARE_TRIGGER_CAMERA // Check for external trigger support TriggerModeInfo triggerModeInfo; error = cam.GetTriggerModeInfo( &triggerModeInfo ; if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } if ( triggerModeInfo.present != true ) { printf( "Camera doesn't support external trigger!\n" ); return -1; }#endif // Get current trigger settings error = cam.GetTriggerMode( &triggerMode ); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } // Set camera to trigger mode 0 triggerMode.onOff = true; triggerMode.mode = 0; triggerMode.parameter = 0;#ifdef SOFTWARE_TRIGGER_CAMERA // A source of 7 means software trigger triggerMode.source = 7;#else // Triggering the camera externally using source 0. triggerMode.source = 0;#endif // Set camera triggering mode error = cam.SetTriggerMode( &triggerMode ); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } // Power on the camera const unsigned int k_cameraPower = 0x610; const unsigned int k_powerVal = 0x80000000; error = cam.WriteRegister( k_cameraPower, k_powerVal ); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } // Poll to ensure camera is ready bool retVal = PollForTriggerReady( &cam ); if( !retVal ) { PrintError( error ); return -1; } // Set camera configuration: region of 24 x 480 pixels // greyscale image mode fmt7ImageSettings.width = col_size; fmt7ImageSettings.height = row_size; fmt7ImageSettings.mode = MODE_0; fmt7ImageSettings.offsetX = 312; fmt7ImageSettings.offsetY = 0; fmt7ImageSettings.pixelFormat = PIXEL_FORMAT_MONO8; // Validate Format 7 settings bool valid; error = cam.ValidateFormat7Settings( &fmt7ImageSettings, &valid, &fmt7PacketInfo ); unsigned int num_bytes = fmt7PacketInfo.recommendedBytesPerPacket; // Set Format 7 (partial image mode) settings error = cam.SetFormat7Configuration( &fmt7ImageSettings, num_bytes ); if ( error != PGRERROR_OK) { PrintError( error ); return -1; } // Start capturing images error = cam.StartCapture(); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } #ifdef SOFTWARE_TRIGGER_CAMERA if ( !CheckSoftwareTriggerPresence( &cam ) ) { printf( "SOFT_ASYNC_TRIGGER not implemented on " "this camera! Stopping application\n" ); return -1; } #else printf( "Trigger the camera by sending a trigger pulse" " to GPIO%d.\n", triggerMode.source ); #endif error = cam.StartCapture(); // Warm up - necessary to get decent images. // See Flea2 Technical Ref.: camera will typically not // send first 2 images acquired after power-up // It may therefore take several (n) images to get // satisfactory image, where n is undefined for ( int i = 0; i < 30; i++ ) { // Check that the trigger is ready PollForTriggerReady( &cam ); // Fire software trigger FireSoftwareTrigger( &cam ); Image im; // Retrieve image before starting main loop Error error = cam.RetrieveBuffer( &im ); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } } #ifdef SOFTWARE_TRIGGER_CAMERA if ( !CheckSoftwareTriggerPresence( &cam ) ) { printf( "SOFT_ASYNC_TRIGGER not implemented on this" " camera! Stopping application\n"); return -1; } #else printf( "Trigger camera by sending trigger pulse to" " GPIO%d.\n", triggerMode.source ); #endif // Grab images acc. to number of hw/sw trigger events for ( int i = 0; i < 25; i++ ) { GrabImages( &cam, img, img_bw, storage, i ); } // Turn trigger mode off. triggerMode.onOff = false; error = cam.SetTriggerMode( &triggerMode ); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } printf( "\nFinished grabbing images\n" ); // Stop capturing images error = cam.StopCapture(); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } // Disconnect the camera error = cam.Disconnect(); if ( error != PGRERROR_OK ) { PrintError( error ); return -1; } ReleaseImage( img, img_bw, storage); return 0;} // Print error tracevoid PrintError( Error error ){ error.PrintErrorTrace();} // Check for the presence of software triggerbool CheckSoftwareTriggerPresence( Camera* pCam ){ const unsigned int k_triggerInq = 0x530; Error error; unsigned int regVal = 0; error = pCam->ReadRegister( k_triggerInq, ®Val ); if ( error != PGRERROR_OK ) { // TODO } if( ( regVal & 0x10000 ) != 0x10000 ) { return false; } return true;}// Start polling for trigger readybool PollForTriggerReady( Camera* pCam ){ const unsigned int k_softwareTrigger = 0x62C; Error error; unsigned int regVal = 0; do { error = pCam->ReadRegister( k_softwareTrigger, regVal ); if ( error != PGRERROR_OK ) { // TODO } } while ( (regVal >> 31) != 0 ); return true;}// Launch the software trigger eventbool FireSoftwareTrigger( Camera* pCam ){ const unsigned int k_softwareTrigger = 0x62C; const unsigned int k_fireVal = 0x80000000; Error error; error = pCam->WriteRegister( k_softwareTrigger, k_fireVal ); if ( error != PGRERROR_OK ) { // TODO } return true;}// Tidy up memory allocated for images etcvoid ReleaseImage( IplImage* pimg, IplImage* pimg_bw, CvMemStorage* pstorage ){ cvReleaseImage( &pimg ); cvReleaseImage( &pimg_bw ); cvClearMemStorage( pstorage );}// Grab camera grayscale image and convert into// an OpenCV imagevoid GrabImages( Camera* pcam, IplImage* pimg, IplImage* pimg_bw, CvMemStorage* pstorage, int cnt ){ Image image; #ifdef SOFTWARE_TRIGGER_CAMERA // Check that the trigger is ready PollForTriggerReady( pcam ); printf( "Press Enter to initiate software trigger.\n" ); getchar(); // Fire software trigger bool retVal = FireSoftwareTrigger( pcam ); if ( !retVal ) { // TODO. } #endif // Retrieve image before starting main loop Error error = pcam->RetrieveBuffer( &image ); if ( error != PGRERROR_OK ) { // TODO. } // Copy FlyCapture2 image into OpenCV struct memcpy( pimg->imageData, image.GetData(), data_size ); // Save the bitmap to file cvSaveImage( "orig.bmp", pimg ); // Threshold to convert image into binary (B&W) cvThreshold( pimg, // source image pimg_bw, // destination image 145, // threhold val. 255, // max. val CV_THRESH_BINARY ); // binary type ); // Save the bitmap to file char buffer[ 20 ]; sprintf( buffer, "%d", cnt ); std::string mess = "B_W.bmp_"; mess.append( buffer ); mess.append( ".bmp" ); cvSaveImage( mess.c_str(), pimg_bw ); // Find connected components using OpenCV // for black spots against a white background CvSeq* seq; int num_blobs = cvFindContours( pimg_bw, pstorage, &seq, sizeof( CvContour ), CV_RETR_LIST, CV_CHAIN_APPROX_NONE, cvPoint( 0, 0 ) ) - 1;} |
Other posts related to image detection
Tracking Coloured Objects in Video using OpenCV
Displaying AVI Video using OpenCV
Analyzing FlyCapture2 Images obtained from Flea2 Cameras
OpenCV Detection of Dark Objects Against Light Backgrounds
Getting Started with OpenCV in Visual Studio
Object Detection Using the OpenCV / cvBlobsLib Libraries
