C++
OPENALPRDLLEXPORT
namespacealpr
Enums
enumAlprHardwareAcceleration
Values:
enumeratorALPR_CPU
enumeratorALPRNVIDIAGPU
classAlpr
Public Functions
Alpr(const std::string country, const std::string configFile, const std::string runtimeDir, const std::string licenseKey)
Initialize the OpenALPR library. This operation should be performed once per thread.
Parameters
country: The country used for recognition (e.g., us for North American, eu for European, br for Brazil, etc.)configFile: The path to the openalpr.conf file. Default is /etc/openalpr/openalpr.confruntimeDir: The path to the runtime_data directory. Default is /usr/share/openalpr/runtime_data/licenseKey: The OpenALPR commercial license key
~Alpr()
Alpr(const std::string country, const std::string configFile = "", const std::string runtimeDir = "")
Deprecated - Legacy constructor to support existing symbols.
Initialize the OpenALPR library. This operation should be performed once per thread. Overrides the configuration in openalpr.conf to set GPU usage explicitly
Parameters
country: The country used for recognition (e.g., us for North American, eu for European, br for Brazil, etc.)configFile: The path to the openalpr.conf file. Default is /etc/openalpr/openalpr.confruntimeDir: The path to the runtime_data directory. Default is /usr/share/openalpr/runtime_data/licenseKey: The OpenALPR commercial license keyacceleration_type: Nvidia GPU or CPUgpu_id: The ID of the GPU to use. Default=0batch_size: The number of images to process on the GPU simultaneously. Default=10
void setCountry(std::string country)
Set the country used for plate recognition
Parameters
country: Country code (e.g., us, eu, in, etc.)
void setPrewarp(std::string prewarp_config)
Parameters
prewarp_config: A specially constructed string produced by the openalpr_calibrate utility
void setMask(unsigned char *pixelData, int bytesPerPixel, int imgWidth, int imgHeight)
Update the detection mask without reloading the library. The detection mask is used to improve processing efficiency (by ignoring areas for recognition) and to reduce false positives (by disqualifying plates found in areas where there could not be plates).
The Mask is simply a black/white image that should match the input resolution of the images. If it does not match, it will be stretched to fit. The white portions are areas that should be included for processing and the black areas will be ignored.
Parameters
pixelData: raw image bytes for BGR channelsbytesPerPixel: Number of bytes for each pixel (e.g., 3)imgWidth: Width of the image in pixelsimgHeight: Height of the image in pixels
void setDetectRegion(bool detectRegion)
Deprecated:
Enables/disables detection of state/province for applicable countries
Parameters
detectRegion: true to enable region detection, false to disable
void setTopN(int topN)
Set the maximum number of plate candidates to return
Parameters
topN: an integer specifying the maximum possible plate results to return (default: 10)
void setDefaultRegion(std::string region)
Specify a region to use when applying patterns. For example, if the camera is installed in Germany, and 90% of the license plates will be German plates, using a pattern of “de” would try to match the results against the German plate patterns and improve accuracy.
Parameters
region: The state/province to use as the default for pattern matching (e.g., md for USA/Maryland, be for Europe/Belgium).
Recognize from an image on disk. The file should be an image in an encoded format such as JPG, PNG, BMP, GIF, etc.
ReturnThe results of the ALPR recognition for this imageParameters
filepath: Location of the file on disk (e.g., /tmp/image.jpg)
Recognize from byte data representing an encoded image (e.g., BMP, PNG, JPG, GIF etc).
ReturnThe results of the ALPR recognition for this imageParameters
imageBytes: array of bytes for the image
Recognize from byte data representing an encoded image (e.g., BMP, PNG, JPG, GIF etc).
ReturnThe results of the ALPR recognition for this imageParameters
imageBytes: Image bytes for the encoded imageregionsOfInterest: an array of regions to recognize. Areas not covered by a region of interest would be ignored. You may pass an empty array to scan the entire image.
Recognize from raw pixel data.
ReturnThe results of the ALPR recognition for this imageParameters
pixelData: raw image bytes for BGR channelsbytesPerPixel: Number of bytes for each pixel (e.g., 3)imgWidth: Width of the image in pixelsimgHeight: Height of the image in pixelsregionsOfInterest: an array of regions to recognize. Areas not covered by a region of interest would be ignored. You may pass an empty array to scan the entire image.
Recognize a batch of images from byte data representing encoded images (e.g., BMP, PNG, JPG, GIF etc).
ReturnThe results of the ALPR recognition for this imageParameters
imageBytes: An array of encoded image bytes
Recognize a batch of images from raw pixel data. Batch processing is recommended when using a GPU for processing. Sending a batch of images allows the GPU to process them in parallel improving the overall efficiency.
ReturnThe results of the ALPR recognition for this imageParameters
pixelData: raw image bytes for BGR channelsbytesPerPixel: Number of bytes for each pixel (e.g., 3)imgWidth: Width of the image in pixelsimgHeight: Height of the image in pixelsnum_images: The number of images in the batchregionsOfInterest: an array of regions to recognize. Areas not covered by a region of interest would be ignored. You may pass an empty array to scan the entire image.
bool isLoaded()
Verifies whether the OpenALPR instance was properly loaded
**Return**true if the engine is ready to use, false otherwise
bool getUseGpu()
int getGpuBatchSize()
int getGpuId()
Config *getConfig()
Public Static Functions
Returna properly formatted JSON string describing the ALPR resultsParameters
std::string getVersion()
Gets the current version of the OpenALPR software
**Return**A version string (e.g., 2.4.102)
Private Members
AlprImpl *impl
structAlprCoordinate
Public Members
int x
int y
structAlprPlate
#include <alpr.h>
An individual plate result.
Public Members
std::string characters
The string characters of the plate (e.g., ABC123)
float overall_confidence
The confidence score from 0-100.
bool matches_template
Whether the plate matches a template for the province.
classAlprPlateResult
Public Functions
AlprPlateResult()
~AlprPlateResult()
std::string toJson(bool serialize_crop = false)
Exports this object to a JSON representation.
Public Members
int requested_topn
The number requested is always >= the topNPlates count.
std::string country
The country (training data code) that was used to recognize the plate.
the best plate is the topNPlate with the highest confidence
A list of possible plate number permutations.
float processingtimems
The processing time for this plate.
the X/Y coordinates of the corners of the plate (clock-wise from top-left)
int plate_index
The index of the plate if there were multiple plates returned.
std::string region
When province detection is enabled, this returns the region (e.g., md).
int regionConfidence
The confidence for the detected region (0-100)
A bounding box where the car is likely to be found.
std::vector<unsigned char> platecropjpeg
A cropped image (encoded as a JPEG) for the plate.
Public Static Functions
Rebuilds this object from a JSON string.
classAlprRegionOfInterest
#include <alpr.h>
Specifies a region of interest to restrict the area that OpenALPR analyzes. The region(s) must be rectangular. The x,y positions are specified in pixels and correspond to the top left corners of the rectangle. The width and height are also specified in pixels. The coordinate system origin (0,0) is the top left of the image
Public Functions
AlprRegionOfInterest()
AlprRegionOfInterest(int x, int y, int width, int height)
Public Members
int x
int y
int width
int height
classAlprResults
Public Functions
AlprResults()
~AlprResults()
std::string toJson(bool serialize_crop = false)
Exports this object to a JSON representation.
Public Members
int64_t epoch_time
The time (in epoch ms) when the image for this image was captured.
int64_t frame_number
The relative frame number for this image.
int img_width
int img_height
float totalprocessingtime_ms
The total processing time for detecting and recognizing all plates in the image.
std::string image_uuid
A globally unique ID for this image.
bool error
True if an error occurred during processing, false otherwise.
std::string error_message
An error message if there was an error processing.
An array of plate results.
The regions of interest provided when requesting recognition.
Public Static Functions
Rebuilds this object from a JSON string.
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