/
imgcodecs.hpp
420 lines (358 loc) · 23.9 KB
/
imgcodecs.hpp
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
420
/*M///////////////////////////////////////////////////////////////////////////////////////
//
// IMPORTANT: READ BEFORE DOWNLOADING, COPYING, INSTALLING OR USING.
//
// By downloading, copying, installing or using the software you agree to this license.
// If you do not agree to this license, do not download, install,
// copy or use the software.
//
//
// License Agreement
// For Open Source Computer Vision Library
//
// Copyright (C) 2000-2008, Intel Corporation, all rights reserved.
// Copyright (C) 2009, Willow Garage Inc., all rights reserved.
// Third party copyrights are property of their respective owners.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
// * Redistribution's of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// * Redistribution's in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// * The name of the copyright holders may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// This software is provided by the copyright holders and contributors "as is" and
// any express or implied warranties, including, but not limited to, the implied
// warranties of merchantability and fitness for a particular purpose are disclaimed.
// In no event shall the Intel Corporation or contributors be liable for any direct,
// indirect, incidental, special, exemplary, or consequential damages
// (including, but not limited to, procurement of substitute goods or services;
// loss of use, data, or profits; or business interruption) however caused
// and on any theory of liability, whether in contract, strict liability,
// or tort (including negligence or otherwise) arising in any way out of
// the use of this software, even if advised of the possibility of such damage.
//
//M*/
#ifndef OPENCV_IMGCODECS_HPP
#define OPENCV_IMGCODECS_HPP
#include "opencv2/core.hpp"
/**
@defgroup imgcodecs Image file reading and writing
@{
@defgroup imgcodecs_flags Flags used for image file reading and writing
@defgroup imgcodecs_ios iOS glue
@defgroup imgcodecs_macosx MacOS(OSX) glue
@}
*/
//////////////////////////////// image codec ////////////////////////////////
namespace cv
{
//! @addtogroup imgcodecs
//! @{
//! @addtogroup imgcodecs_flags
//! @{
//! Imread flags
enum ImreadModes {
IMREAD_UNCHANGED = -1, //!< If set, return the loaded image as is (with alpha channel, otherwise it gets cropped). Ignore EXIF orientation.
IMREAD_GRAYSCALE = 0, //!< If set, always convert image to the single channel grayscale image (codec internal conversion).
IMREAD_COLOR = 1, //!< If set, always convert image to the 3 channel BGR color image.
IMREAD_ANYDEPTH = 2, //!< If set, return 16-bit/32-bit image when the input has the corresponding depth, otherwise convert it to 8-bit.
IMREAD_ANYCOLOR = 4, //!< If set, the image is read in any possible color format.
IMREAD_LOAD_GDAL = 8, //!< If set, use the gdal driver for loading the image.
IMREAD_REDUCED_GRAYSCALE_2 = 16, //!< If set, always convert image to the single channel grayscale image and the image size reduced 1/2.
IMREAD_REDUCED_COLOR_2 = 17, //!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/2.
IMREAD_REDUCED_GRAYSCALE_4 = 32, //!< If set, always convert image to the single channel grayscale image and the image size reduced 1/4.
IMREAD_REDUCED_COLOR_4 = 33, //!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/4.
IMREAD_REDUCED_GRAYSCALE_8 = 64, //!< If set, always convert image to the single channel grayscale image and the image size reduced 1/8.
IMREAD_REDUCED_COLOR_8 = 65, //!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/8.
IMREAD_IGNORE_ORIENTATION = 128 //!< If set, do not rotate the image according to EXIF's orientation flag.
};
//! Imwrite flags
enum ImwriteFlags {
IMWRITE_JPEG_QUALITY = 1, //!< For JPEG, it can be a quality from 0 to 100 (the higher is the better). Default value is 95.
IMWRITE_JPEG_PROGRESSIVE = 2, //!< Enable JPEG features, 0 or 1, default is False.
IMWRITE_JPEG_OPTIMIZE = 3, //!< Enable JPEG features, 0 or 1, default is False.
IMWRITE_JPEG_RST_INTERVAL = 4, //!< JPEG restart interval, 0 - 65535, default is 0 - no restart.
IMWRITE_JPEG_LUMA_QUALITY = 5, //!< Separate luma quality level, 0 - 100, default is -1 - don't use.
IMWRITE_JPEG_CHROMA_QUALITY = 6, //!< Separate chroma quality level, 0 - 100, default is -1 - don't use.
IMWRITE_JPEG_SAMPLING_FACTOR = 7, //!< For JPEG, set sampling factor. See cv::ImwriteJPEGSamplingFactorParams.
IMWRITE_PNG_COMPRESSION = 16, //!< For PNG, it can be the compression level from 0 to 9. A higher value means a smaller size and longer compression time. If specified, strategy is changed to IMWRITE_PNG_STRATEGY_DEFAULT (Z_DEFAULT_STRATEGY). Default value is 1 (best speed setting).
IMWRITE_PNG_STRATEGY = 17, //!< One of cv::ImwritePNGFlags, default is IMWRITE_PNG_STRATEGY_RLE.
IMWRITE_PNG_BILEVEL = 18, //!< Binary level PNG, 0 or 1, default is 0.
IMWRITE_PXM_BINARY = 32, //!< For PPM, PGM, or PBM, it can be a binary format flag, 0 or 1. Default value is 1.
IMWRITE_EXR_TYPE = (3 << 4) + 0 /* 48 */, //!< override EXR storage type (FLOAT (FP32) is default)
IMWRITE_EXR_COMPRESSION = (3 << 4) + 1 /* 49 */, //!< override EXR compression type (ZIP_COMPRESSION = 3 is default)
IMWRITE_EXR_DWA_COMPRESSION_LEVEL = (3 << 4) + 2 /* 50 */, //!< override EXR DWA compression level (45 is default)
IMWRITE_WEBP_QUALITY = 64, //!< For WEBP, it can be a quality from 1 to 100 (the higher is the better). By default (without any parameter) and for quality above 100 the lossless compression is used.
IMWRITE_HDR_COMPRESSION = (5 << 4) + 0 /* 80 */, //!< specify HDR compression
IMWRITE_PAM_TUPLETYPE = 128,//!< For PAM, sets the TUPLETYPE field to the corresponding string value that is defined for the format
IMWRITE_TIFF_RESUNIT = 256,//!< For TIFF, use to specify which DPI resolution unit to set; see libtiff documentation for valid values
IMWRITE_TIFF_XDPI = 257,//!< For TIFF, use to specify the X direction DPI
IMWRITE_TIFF_YDPI = 258,//!< For TIFF, use to specify the Y direction DPI
IMWRITE_TIFF_COMPRESSION = 259,//!< For TIFF, use to specify the image compression scheme. See libtiff for integer constants corresponding to compression formats. Note, for images whose depth is CV_32F, only libtiff's SGILOG compression scheme is used. For other supported depths, the compression scheme can be specified by this flag; LZW compression is the default.
IMWRITE_JPEG2000_COMPRESSION_X1000 = 272,//!< For JPEG2000, use to specify the target compression rate (multiplied by 1000). The value can be from 0 to 1000. Default is 1000.
IMWRITE_AVIF_QUALITY = 512,//!< For AVIF, it can be a quality between 0 and 100 (the higher the better). Default is 95.
IMWRITE_AVIF_DEPTH = 513,//!< For AVIF, it can be 8, 10 or 12. If >8, it is stored/read as CV_32F. Default is 8.
IMWRITE_AVIF_SPEED = 514 //!< For AVIF, it is between 0 (slowest) and (fastest). Default is 9.
};
enum ImwriteJPEGSamplingFactorParams {
IMWRITE_JPEG_SAMPLING_FACTOR_411 = 0x411111, //!< 4x1,1x1,1x1
IMWRITE_JPEG_SAMPLING_FACTOR_420 = 0x221111, //!< 2x2,1x1,1x1(Default)
IMWRITE_JPEG_SAMPLING_FACTOR_422 = 0x211111, //!< 2x1,1x1,1x1
IMWRITE_JPEG_SAMPLING_FACTOR_440 = 0x121111, //!< 1x2,1x1,1x1
IMWRITE_JPEG_SAMPLING_FACTOR_444 = 0x111111 //!< 1x1,1x1,1x1(No subsampling)
};
enum ImwriteEXRTypeFlags {
/*IMWRITE_EXR_TYPE_UNIT = 0, //!< not supported */
IMWRITE_EXR_TYPE_HALF = 1, //!< store as HALF (FP16)
IMWRITE_EXR_TYPE_FLOAT = 2 //!< store as FP32 (default)
};
enum ImwriteEXRCompressionFlags {
IMWRITE_EXR_COMPRESSION_NO = 0, //!< no compression
IMWRITE_EXR_COMPRESSION_RLE = 1, //!< run length encoding
IMWRITE_EXR_COMPRESSION_ZIPS = 2, //!< zlib compression, one scan line at a time
IMWRITE_EXR_COMPRESSION_ZIP = 3, //!< zlib compression, in blocks of 16 scan lines
IMWRITE_EXR_COMPRESSION_PIZ = 4, //!< piz-based wavelet compression
IMWRITE_EXR_COMPRESSION_PXR24 = 5, //!< lossy 24-bit float compression
IMWRITE_EXR_COMPRESSION_B44 = 6, //!< lossy 4-by-4 pixel block compression, fixed compression rate
IMWRITE_EXR_COMPRESSION_B44A = 7, //!< lossy 4-by-4 pixel block compression, flat fields are compressed more
IMWRITE_EXR_COMPRESSION_DWAA = 8, //!< lossy DCT based compression, in blocks of 32 scanlines. More efficient for partial buffer access. Supported since OpenEXR 2.2.0.
IMWRITE_EXR_COMPRESSION_DWAB = 9, //!< lossy DCT based compression, in blocks of 256 scanlines. More efficient space wise and faster to decode full frames than DWAA_COMPRESSION. Supported since OpenEXR 2.2.0.
};
//! Imwrite PNG specific flags used to tune the compression algorithm.
/** These flags will be modify the way of PNG image compression and will be passed to the underlying zlib processing stage.
- The effect of IMWRITE_PNG_STRATEGY_FILTERED is to force more Huffman coding and less string matching; it is somewhat intermediate between IMWRITE_PNG_STRATEGY_DEFAULT and IMWRITE_PNG_STRATEGY_HUFFMAN_ONLY.
- IMWRITE_PNG_STRATEGY_RLE is designed to be almost as fast as IMWRITE_PNG_STRATEGY_HUFFMAN_ONLY, but give better compression for PNG image data.
- The strategy parameter only affects the compression ratio but not the correctness of the compressed output even if it is not set appropriately.
- IMWRITE_PNG_STRATEGY_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler decoder for special applications.
*/
enum ImwritePNGFlags {
IMWRITE_PNG_STRATEGY_DEFAULT = 0, //!< Use this value for normal data.
IMWRITE_PNG_STRATEGY_FILTERED = 1, //!< Use this value for data produced by a filter (or predictor).Filtered data consists mostly of small values with a somewhat random distribution. In this case, the compression algorithm is tuned to compress them better.
IMWRITE_PNG_STRATEGY_HUFFMAN_ONLY = 2, //!< Use this value to force Huffman encoding only (no string match).
IMWRITE_PNG_STRATEGY_RLE = 3, //!< Use this value to limit match distances to one (run-length encoding).
IMWRITE_PNG_STRATEGY_FIXED = 4 //!< Using this value prevents the use of dynamic Huffman codes, allowing for a simpler decoder for special applications.
};
//! Imwrite PAM specific tupletype flags used to define the 'TUPLETYPE' field of a PAM file.
enum ImwritePAMFlags {
IMWRITE_PAM_FORMAT_NULL = 0,
IMWRITE_PAM_FORMAT_BLACKANDWHITE = 1,
IMWRITE_PAM_FORMAT_GRAYSCALE = 2,
IMWRITE_PAM_FORMAT_GRAYSCALE_ALPHA = 3,
IMWRITE_PAM_FORMAT_RGB = 4,
IMWRITE_PAM_FORMAT_RGB_ALPHA = 5
};
//! Imwrite HDR specific values for IMWRITE_HDR_COMPRESSION parameter key
enum ImwriteHDRCompressionFlags {
IMWRITE_HDR_COMPRESSION_NONE = 0,
IMWRITE_HDR_COMPRESSION_RLE = 1
};
//! @} imgcodecs_flags
/** @brief Loads an image from a file.
@anchor imread
The function imread loads an image from the specified file and returns it. If the image cannot be
read (because of missing file, improper permissions, unsupported or invalid format), the function
returns an empty matrix ( Mat::data==NULL ).
Currently, the following file formats are supported:
- Windows bitmaps - \*.bmp, \*.dib (always supported)
- JPEG files - \*.jpeg, \*.jpg, \*.jpe (see the *Note* section)
- JPEG 2000 files - \*.jp2 (see the *Note* section)
- Portable Network Graphics - \*.png (see the *Note* section)
- WebP - \*.webp (see the *Note* section)
- AVIF - \*.avif (see the *Note* section)
- Portable image format - \*.pbm, \*.pgm, \*.ppm \*.pxm, \*.pnm (always supported)
- PFM files - \*.pfm (see the *Note* section)
- Sun rasters - \*.sr, \*.ras (always supported)
- TIFF files - \*.tiff, \*.tif (see the *Note* section)
- OpenEXR Image files - \*.exr (see the *Note* section)
- Radiance HDR - \*.hdr, \*.pic (always supported)
- Raster and Vector geospatial data supported by GDAL (see the *Note* section)
@note
- The function determines the type of an image by the content, not by the file extension.
- In the case of color images, the decoded images will have the channels stored in **B G R** order.
- When using IMREAD_GRAYSCALE, the codec's internal grayscale conversion will be used, if available.
Results may differ to the output of cvtColor()
- On Microsoft Windows\* OS and MacOSX\*, the codecs shipped with an OpenCV image (libjpeg,
libpng, libtiff, and libjasper) are used by default. So, OpenCV can always read JPEGs, PNGs,
and TIFFs. On MacOSX, there is also an option to use native MacOSX image readers. But beware
that currently these native image loaders give images with different pixel values because of
the color management embedded into MacOSX.
- On Linux\*, BSD flavors and other Unix-like open-source operating systems, OpenCV looks for
codecs supplied with an OS image. Install the relevant packages (do not forget the development
files, for example, "libjpeg-dev", in Debian\* and Ubuntu\*) to get the codec support or turn
on the OPENCV_BUILD_3RDPARTY_LIBS flag in CMake.
- In the case you set *WITH_GDAL* flag to true in CMake and @ref IMREAD_LOAD_GDAL to load the image,
then the [GDAL](http://www.gdal.org) driver will be used in order to decode the image, supporting
the following formats: [Raster](http://www.gdal.org/formats_list.html),
[Vector](http://www.gdal.org/ogr_formats.html).
- If EXIF information is embedded in the image file, the EXIF orientation will be taken into account
and thus the image will be rotated accordingly except if the flags @ref IMREAD_IGNORE_ORIENTATION
or @ref IMREAD_UNCHANGED are passed.
- Use the IMREAD_UNCHANGED flag to keep the floating point values from PFM image.
- By default number of pixels must be less than 2^30. Limit can be set using system
variable OPENCV_IO_MAX_IMAGE_PIXELS
@param filename Name of file to be loaded.
@param flags Flag that can take values of cv::ImreadModes
*/
CV_EXPORTS_W Mat imread( const String& filename, int flags = IMREAD_COLOR );
/** @brief Loads a multi-page image from a file.
The function imreadmulti loads a multi-page image from the specified file into a vector of Mat objects.
@param filename Name of file to be loaded.
@param mats A vector of Mat objects holding each page.
@param flags Flag that can take values of cv::ImreadModes, default with cv::IMREAD_ANYCOLOR.
@sa cv::imread
*/
CV_EXPORTS_W bool imreadmulti(const String& filename, CV_OUT std::vector<Mat>& mats, int flags = IMREAD_ANYCOLOR);
/** @brief Loads a of images of a multi-page image from a file.
The function imreadmulti loads a specified range from a multi-page image from the specified file into a vector of Mat objects.
@param filename Name of file to be loaded.
@param mats A vector of Mat objects holding each page.
@param start Start index of the image to load
@param count Count number of images to load
@param flags Flag that can take values of cv::ImreadModes, default with cv::IMREAD_ANYCOLOR.
@sa cv::imread
*/
CV_EXPORTS_W bool imreadmulti(const String& filename, CV_OUT std::vector<Mat>& mats, int start, int count, int flags = IMREAD_ANYCOLOR);
/** @brief Returns the number of images inside the give file
The function imcount will return the number of pages in a multi-page image, or 1 for single-page images
@param filename Name of file to be loaded.
@param flags Flag that can take values of cv::ImreadModes, default with cv::IMREAD_ANYCOLOR.
*/
CV_EXPORTS_W size_t imcount(const String& filename, int flags = IMREAD_ANYCOLOR);
/** @brief Saves an image to a specified file.
The function imwrite saves the image to the specified file. The image format is chosen based on the
filename extension (see cv::imread for the list of extensions). In general, only 8-bit unsigned (CV_8U)
single-channel or 3-channel (with 'BGR' channel order) images
can be saved using this function, with these exceptions:
- With OpenEXR encoder, only 32-bit float (CV_32F) images can be saved.
- 8-bit unsigned (CV_8U) images are not supported.
- With Radiance HDR encoder, non 64-bit float (CV_64F) images can be saved.
- All images will be converted to 32-bit float (CV_32F).
- With JPEG 2000 encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- With PAM encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- With PNG encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- PNG images with an alpha channel can be saved using this function. To do this, create
8-bit (or 16-bit) 4-channel image BGRA, where the alpha channel goes last. Fully transparent pixels
should have alpha set to 0, fully opaque pixels should have alpha set to 255/65535 (see the code sample below).
- With PGM/PPM encoder, 8-bit unsigned (CV_8U) and 16-bit unsigned (CV_16U) images can be saved.
- With TIFF encoder, 8-bit unsigned (CV_8U), 16-bit unsigned (CV_16U),
32-bit float (CV_32F) and 64-bit float (CV_64F) images can be saved.
- Multiple images (vector of Mat) can be saved in TIFF format (see the code sample below).
- 32-bit float 3-channel (CV_32FC3) TIFF images will be saved
using the LogLuv high dynamic range encoding (4 bytes per pixel)
If the image format is not supported, the image will be converted to 8-bit unsigned (CV_8U) and saved that way.
If the format, depth or channel order is different, use
Mat::convertTo and cv::cvtColor to convert it before saving. Or, use the universal FileStorage I/O
functions to save the image to XML or YAML format.
The sample below shows how to create a BGRA image, how to set custom compression parameters and save it to a PNG file.
It also demonstrates how to save multiple images in a TIFF file:
@include snippets/imgcodecs_imwrite.cpp
@param filename Name of the file.
@param img (Mat or vector of Mat) Image or Images to be saved.
@param params Format-specific parameters encoded as pairs (paramId_1, paramValue_1, paramId_2, paramValue_2, ... .) see cv::ImwriteFlags
*/
CV_EXPORTS_W bool imwrite( const String& filename, InputArray img,
const std::vector<int>& params = std::vector<int>());
//! @brief multi-image overload for bindings
CV_WRAP static inline
bool imwritemulti(const String& filename, InputArrayOfArrays img,
const std::vector<int>& params = std::vector<int>())
{
return imwrite(filename, img, params);
}
/** @brief Reads an image from a buffer in memory.
The function imdecode reads an image from the specified buffer in the memory. If the buffer is too short or
contains invalid data, the function returns an empty matrix ( Mat::data==NULL ).
See cv::imread for the list of supported formats and flags description.
@note In the case of color images, the decoded images will have the channels stored in **B G R** order.
@param buf Input array or vector of bytes.
@param flags The same flags as in cv::imread, see cv::ImreadModes.
*/
CV_EXPORTS_W Mat imdecode( InputArray buf, int flags );
/** @overload
@param buf Input array or vector of bytes.
@param flags The same flags as in cv::imread, see cv::ImreadModes.
@param dst The optional output placeholder for the decoded matrix. It can save the image
reallocations when the function is called repeatedly for images of the same size. In case of decoder
failure the function returns empty cv::Mat object, but does not release user-provided dst buffer.
*/
CV_EXPORTS Mat imdecode( InputArray buf, int flags, Mat* dst);
/** @brief Reads a multi-page image from a buffer in memory.
The function imdecodemulti reads a multi-page image from the specified buffer in the memory. If the buffer is too short or
contains invalid data, the function returns false.
See cv::imreadmulti for the list of supported formats and flags description.
@note In the case of color images, the decoded images will have the channels stored in **B G R** order.
@param buf Input array or vector of bytes.
@param flags The same flags as in cv::imread, see cv::ImreadModes.
@param mats A vector of Mat objects holding each page, if more than one.
@param range A continuous selection of pages.
*/
CV_EXPORTS_W bool imdecodemulti(InputArray buf, int flags, CV_OUT std::vector<Mat>& mats, const cv::Range& range = Range::all());
/** @brief Encodes an image into a memory buffer.
The function imencode compresses the image and stores it in the memory buffer that is resized to fit the
result. See cv::imwrite for the list of supported formats and flags description.
@param ext File extension that defines the output format. Must include a leading period.
@param img Image to be written.
@param buf Output buffer resized to fit the compressed image.
@param params Format-specific parameters. See cv::imwrite and cv::ImwriteFlags.
*/
CV_EXPORTS_W bool imencode( const String& ext, InputArray img,
CV_OUT std::vector<uchar>& buf,
const std::vector<int>& params = std::vector<int>());
/** @brief Returns true if the specified image can be decoded by OpenCV
@param filename File name of the image
*/
CV_EXPORTS_W bool haveImageReader( const String& filename );
/** @brief Returns true if an image with the specified filename can be encoded by OpenCV
@param filename File name of the image
*/
CV_EXPORTS_W bool haveImageWriter( const String& filename );
/** @brief To read Multi Page images on demand
The ImageCollection class provides iterator API to read multi page images on demand. Create iterator
to the collection of the images and iterate over the collection. Decode the necessary page with operator*.
The performance of page decoding is O(1) if collection is increment sequentially. If the user wants to access random page,
then the time Complexity is O(n) because the collection has to be reinitialized every time in order to go to the correct page.
However, the intermediate pages are not decoded during the process, so typically it's quite fast.
This is required because multipage codecs does not support going backwards.
After decoding the one page, it is stored inside the collection cache. Hence, trying to get Mat object from already decoded page is O(1).
If you need memory, you can use .releaseCache() method to release cached index.
The space complexity is O(n) if all pages are decoded into memory. The user is able to decode and release images on demand.
*/
class CV_EXPORTS ImageCollection {
public:
struct CV_EXPORTS iterator {
iterator(ImageCollection* col);
iterator(ImageCollection* col, int end);
Mat& operator*();
Mat* operator->();
iterator& operator++();
iterator operator++(int);
friend bool operator== (const iterator& a, const iterator& b) { return a.m_curr == b.m_curr; }
friend bool operator!= (const iterator& a, const iterator& b) { return a.m_curr != b.m_curr; }
private:
ImageCollection* m_pCollection;
int m_curr;
};
ImageCollection();
ImageCollection(const String& filename, int flags);
void init(const String& img, int flags);
size_t size() const;
const Mat& at(int index);
const Mat& operator[](int index);
void releaseCache(int index);
iterator begin();
iterator end();
class Impl;
Ptr<Impl> getImpl();
protected:
Ptr<Impl> pImpl;
};
//! @} imgcodecs
} // cv
#endif //OPENCV_IMGCODECS_HPP