tesseract 4.1.1
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tesseract::ImageThresholder Class Reference

#include <thresholder.h>

Public Member Functions

 ImageThresholder ()
 
virtual ~ImageThresholder ()
 
virtual void Clear ()
 Destroy the Pix if there is one, freeing memory. More...
 
bool IsEmpty () const
 Return true if no image has been set. More...
 
void SetImage (const unsigned char *imagedata, int width, int height, int bytes_per_pixel, int bytes_per_line)
 
void SetRectangle (int left, int top, int width, int height)
 
virtual void GetImageSizes (int *left, int *top, int *width, int *height, int *imagewidth, int *imageheight)
 
bool IsColor () const
 Return true if the source image is color. More...
 
bool IsBinary () const
 Returns true if the source image is binary. More...
 
int GetScaleFactor () const
 
void SetSourceYResolution (int ppi)
 
int GetSourceYResolution () const
 
int GetScaledYResolution () const
 
void SetEstimatedResolution (int ppi)
 
int GetScaledEstimatedResolution () const
 
void SetImage (const Pix *pix)
 
virtual bool ThresholdToPix (PageSegMode pageseg_mode, Pix **pix)
 Returns false on error. More...
 
virtual Pix * GetPixRectThresholds ()
 
Pix * GetPixRect ()
 
virtual Pix * GetPixRectGrey ()
 

Protected Member Functions

virtual void Init ()
 Common initialization shared between SetImage methods. More...
 
bool IsFullImage () const
 Return true if we are processing the full image. More...
 
void OtsuThresholdRectToPix (Pix *src_pix, Pix **out_pix) const
 
void ThresholdRectToPix (Pix *src_pix, int num_channels, const int *thresholds, const int *hi_values, Pix **pix) const
 

Protected Attributes

Pix * pix_
 
int image_width_
 Width of source pix_. More...
 
int image_height_
 Height of source pix_. More...
 
int pix_channels_
 Number of 8-bit channels in pix_. More...
 
int pix_wpl_
 Words per line of pix_. More...
 
int scale_
 Scale factor from original image. More...
 
int yres_
 y pixels/inch in source image. More...
 
int estimated_res_
 Resolution estimate from text size. More...
 
int rect_left_
 
int rect_top_
 
int rect_width_
 
int rect_height_
 

Detailed Description

Base class for all tesseract image thresholding classes. Specific classes can add new thresholding methods by overriding ThresholdToPix. Each instance deals with a single image, but the design is intended to be useful for multiple calls to SetRectangle and ThresholdTo* if desired.

Definition at line 35 of file thresholder.h.

Constructor & Destructor Documentation

◆ ImageThresholder()

tesseract::ImageThresholder::ImageThresholder ( )

Definition at line 35 of file thresholder.cpp.

36 : pix_(nullptr),
39 scale_(1), yres_(300), estimated_res_(300) {
40 SetRectangle(0, 0, 0, 0);
41}
int pix_wpl_
Words per line of pix_.
Definition: thresholder.h:176
int estimated_res_
Resolution estimate from text size.
Definition: thresholder.h:180
void SetRectangle(int left, int top, int width, int height)
int scale_
Scale factor from original image.
Definition: thresholder.h:178
int pix_channels_
Number of 8-bit channels in pix_.
Definition: thresholder.h:175
int yres_
y pixels/inch in source image.
Definition: thresholder.h:179
int image_width_
Width of source pix_.
Definition: thresholder.h:173
int image_height_
Height of source pix_.
Definition: thresholder.h:174

◆ ~ImageThresholder()

tesseract::ImageThresholder::~ImageThresholder ( )
virtual

Definition at line 43 of file thresholder.cpp.

43 {
44 Clear();
45}
virtual void Clear()
Destroy the Pix if there is one, freeing memory.
Definition: thresholder.cpp:48

Member Function Documentation

◆ Clear()

void tesseract::ImageThresholder::Clear ( )
virtual

Destroy the Pix if there is one, freeing memory.

Definition at line 48 of file thresholder.cpp.

48 {
49 pixDestroy(&pix_);
50}

◆ GetImageSizes()

void tesseract::ImageThresholder::GetImageSizes ( int *  left,
int *  top,
int *  width,
int *  height,
int *  imagewidth,
int *  imageheight 
)
virtual

Get enough parameters to be able to rebuild bounding boxes in the original image (not just within the rectangle). Left and top are enough with top-down coordinates, but the height of the rectangle and the image are needed for bottom-up.

Definition at line 134 of file thresholder.cpp.

136 {
137 *left = rect_left_;
138 *top = rect_top_;
139 *width = rect_width_;
140 *height = rect_height_;
141 *imagewidth = image_width_;
142 *imageheight = image_height_;
143}

◆ GetPixRect()

Pix * tesseract::ImageThresholder::GetPixRect ( )

Get a clone/copy of the source image rectangle. The returned Pix must be pixDestroyed. This function will be used in the future by the page layout analysis, and the layout analysis that uses it will only be available with Leptonica, so there is no raw equivalent.

Definition at line 236 of file thresholder.cpp.

236 {
237 if (IsFullImage()) {
238 // Just clone the whole thing.
239 return pixClone(pix_);
240 } else {
241 // Crop to the given rectangle.
242 Box* box = boxCreate(rect_left_, rect_top_, rect_width_, rect_height_);
243 Pix* cropped = pixClipRectangle(pix_, box, nullptr);
244 boxDestroy(&box);
245 return cropped;
246 }
247}
bool IsFullImage() const
Return true if we are processing the full image.
Definition: thresholder.h:152

◆ GetPixRectGrey()

Pix * tesseract::ImageThresholder::GetPixRectGrey ( )
virtual

Definition at line 253 of file thresholder.cpp.

253 {
254 Pix* pix = GetPixRect(); // May have to be reduced to grey.
255 int depth = pixGetDepth(pix);
256 if (depth != 8) {
257 Pix* result = depth < 8 ? pixConvertTo8(pix, false)
258 : pixConvertRGBToLuminance(pix);
259 pixDestroy(&pix);
260 return result;
261 }
262 return pix;
263}

◆ GetPixRectThresholds()

Pix * tesseract::ImageThresholder::GetPixRectThresholds ( )
virtual

Definition at line 209 of file thresholder.cpp.

209 {
210 if (IsBinary()) return nullptr;
211 Pix* pix_grey = GetPixRectGrey();
212 int width = pixGetWidth(pix_grey);
213 int height = pixGetHeight(pix_grey);
214 int* thresholds;
215 int* hi_values;
216 OtsuThreshold(pix_grey, 0, 0, width, height, &thresholds, &hi_values);
217 pixDestroy(&pix_grey);
218 Pix* pix_thresholds = pixCreate(width, height, 8);
219 int threshold = thresholds[0] > 0 ? thresholds[0] : 128;
220 pixSetAllArbitrary(pix_thresholds, threshold);
221 delete [] thresholds;
222 delete [] hi_values;
223 return pix_thresholds;
224}
int OtsuThreshold(Pix *src_pix, int left, int top, int width, int height, int **thresholds, int **hi_values)
Definition: otsuthr.cpp:40
virtual Pix * GetPixRectGrey()
bool IsBinary() const
Returns true if the source image is binary.
Definition: thresholder.h:74

◆ GetScaledEstimatedResolution()

int tesseract::ImageThresholder::GetScaledEstimatedResolution ( ) const
inline

Definition at line 105 of file thresholder.h.

105 {
106 return scale_ * estimated_res_;
107 }

◆ GetScaledYResolution()

int tesseract::ImageThresholder::GetScaledYResolution ( ) const
inline

Definition at line 92 of file thresholder.h.

92 {
93 return scale_ * yres_;
94 }

◆ GetScaleFactor()

int tesseract::ImageThresholder::GetScaleFactor ( ) const
inline

Definition at line 78 of file thresholder.h.

78 {
79 return scale_;
80 }

◆ GetSourceYResolution()

int tesseract::ImageThresholder::GetSourceYResolution ( ) const
inline

Definition at line 89 of file thresholder.h.

89 {
90 return yres_;
91 }

◆ Init()

void tesseract::ImageThresholder::Init ( )
protectedvirtual

Common initialization shared between SetImage methods.

Definition at line 227 of file thresholder.cpp.

227 {
229}

◆ IsBinary()

bool tesseract::ImageThresholder::IsBinary ( ) const
inline

Returns true if the source image is binary.

Definition at line 74 of file thresholder.h.

74 {
75 return pix_channels_ == 0;
76 }

◆ IsColor()

bool tesseract::ImageThresholder::IsColor ( ) const
inline

Return true if the source image is color.

Definition at line 69 of file thresholder.h.

69 {
70 return pix_channels_ >= 3;
71 }

◆ IsEmpty()

bool tesseract::ImageThresholder::IsEmpty ( ) const

Return true if no image has been set.

Definition at line 53 of file thresholder.cpp.

53 {
54 return pix_ == nullptr;
55}

◆ IsFullImage()

bool tesseract::ImageThresholder::IsFullImage ( ) const
inlineprotected

Return true if we are processing the full image.

Definition at line 152 of file thresholder.h.

152 {
153 return rect_left_ == 0 && rect_top_ == 0 &&
155 }

◆ OtsuThresholdRectToPix()

void tesseract::ImageThresholder::OtsuThresholdRectToPix ( Pix *  src_pix,
Pix **  out_pix 
) const
protected

Definition at line 266 of file thresholder.cpp.

267 {
268 int* thresholds;
269 int* hi_values;
270
271 int num_channels = OtsuThreshold(src_pix, rect_left_, rect_top_, rect_width_,
272 rect_height_, &thresholds, &hi_values);
273 // only use opencl if compiled w/ OpenCL and selected device is opencl
274#ifdef USE_OPENCL
275 OpenclDevice od;
276 if (num_channels == 4 &&
277 od.selectedDeviceIsOpenCL() && rect_top_ == 0 && rect_left_ == 0) {
278 od.ThresholdRectToPixOCL((unsigned char*)pixGetData(src_pix), num_channels,
279 pixGetWpl(src_pix) * 4, thresholds, hi_values,
280 out_pix /*pix_OCL*/, rect_height_, rect_width_,
282 } else {
283#endif
284 ThresholdRectToPix(src_pix, num_channels, thresholds, hi_values, out_pix);
285#ifdef USE_OPENCL
286 }
287#endif
288 delete [] thresholds;
289 delete [] hi_values;
290}
void ThresholdRectToPix(Pix *src_pix, int num_channels, const int *thresholds, const int *hi_values, Pix **pix) const

◆ SetEstimatedResolution()

void tesseract::ImageThresholder::SetEstimatedResolution ( int  ppi)
inline

Definition at line 100 of file thresholder.h.

100 {
101 estimated_res_ = ppi;
102 }

◆ SetImage() [1/2]

void tesseract::ImageThresholder::SetImage ( const Pix *  pix)

Pix vs raw, which to use? Pix is the preferred input for efficiency, since raw buffers are copied. SetImage for Pix clones its input, so the source pix may be pixDestroyed immediately after, but may not go away until after the Thresholder has finished with it.

Definition at line 150 of file thresholder.cpp.

150 {
151 if (pix_ != nullptr)
152 pixDestroy(&pix_);
153 Pix* src = const_cast<Pix*>(pix);
154 int depth;
155 pixGetDimensions(src, &image_width_, &image_height_, &depth);
156 // Convert the image as necessary so it is one of binary, plain RGB, or
157 // 8 bit with no colormap. Guarantee that we always end up with our own copy,
158 // not just a clone of the input.
159 if (pixGetColormap(src)) {
160 Pix* tmp = pixRemoveColormap(src, REMOVE_CMAP_BASED_ON_SRC);
161 depth = pixGetDepth(tmp);
162 if (depth > 1 && depth < 8) {
163 pix_ = pixConvertTo8(tmp, false);
164 pixDestroy(&tmp);
165 } else {
166 pix_ = tmp;
167 }
168 } else if (depth > 1 && depth < 8) {
169 pix_ = pixConvertTo8(src, false);
170 } else {
171 pix_ = pixCopy(nullptr, src);
172 }
173 depth = pixGetDepth(pix_);
174 pix_channels_ = depth / 8;
175 pix_wpl_ = pixGetWpl(pix_);
176 scale_ = 1;
177 estimated_res_ = yres_ = pixGetYRes(pix_);
178 Init();
179}
virtual void Init()
Common initialization shared between SetImage methods.

◆ SetImage() [2/2]

void tesseract::ImageThresholder::SetImage ( const unsigned char *  imagedata,
int  width,
int  height,
int  bytes_per_pixel,
int  bytes_per_line 
)

SetImage makes a copy of all the image data, so it may be deleted immediately after this call. Greyscale of 8 and color of 24 or 32 bits per pixel may be given. Palette color images will not work properly and must be converted to 24 bit. Binary images of 1 bit per pixel may also be given but they must be byte packed with the MSB of the first byte being the first pixel, and a one pixel is WHITE. For binary images set bytes_per_pixel=0.

Definition at line 65 of file thresholder.cpp.

67 {
68 int bpp = bytes_per_pixel * 8;
69 if (bpp == 0) bpp = 1;
70 Pix* pix = pixCreate(width, height, bpp == 24 ? 32 : bpp);
71 l_uint32* data = pixGetData(pix);
72 int wpl = pixGetWpl(pix);
73 switch (bpp) {
74 case 1:
75 for (int y = 0; y < height; ++y, data += wpl, imagedata += bytes_per_line) {
76 for (int x = 0; x < width; ++x) {
77 if (imagedata[x / 8] & (0x80 >> (x % 8)))
78 CLEAR_DATA_BIT(data, x);
79 else
80 SET_DATA_BIT(data, x);
81 }
82 }
83 break;
84
85 case 8:
86 // Greyscale just copies the bytes in the right order.
87 for (int y = 0; y < height; ++y, data += wpl, imagedata += bytes_per_line) {
88 for (int x = 0; x < width; ++x)
89 SET_DATA_BYTE(data, x, imagedata[x]);
90 }
91 break;
92
93 case 24:
94 // Put the colors in the correct places in the line buffer.
95 for (int y = 0; y < height; ++y, imagedata += bytes_per_line) {
96 for (int x = 0; x < width; ++x, ++data) {
97 SET_DATA_BYTE(data, COLOR_RED, imagedata[3 * x]);
98 SET_DATA_BYTE(data, COLOR_GREEN, imagedata[3 * x + 1]);
99 SET_DATA_BYTE(data, COLOR_BLUE, imagedata[3 * x + 2]);
100 }
101 }
102 break;
103
104 case 32:
105 // Maintain byte order consistency across different endianness.
106 for (int y = 0; y < height; ++y, imagedata += bytes_per_line, data += wpl) {
107 for (int x = 0; x < width; ++x) {
108 data[x] = (imagedata[x * 4] << 24) | (imagedata[x * 4 + 1] << 16) |
109 (imagedata[x * 4 + 2] << 8) | imagedata[x * 4 + 3];
110 }
111 }
112 break;
113
114 default:
115 tprintf("Cannot convert RAW image to Pix with bpp = %d\n", bpp);
116 }
117 SetImage(pix);
118 pixDestroy(&pix);
119}
DLLSYM void tprintf(const char *format,...)
Definition: tprintf.cpp:35
void SetImage(const unsigned char *imagedata, int width, int height, int bytes_per_pixel, int bytes_per_line)
Definition: thresholder.cpp:65

◆ SetRectangle()

void tesseract::ImageThresholder::SetRectangle ( int  left,
int  top,
int  width,
int  height 
)

Store the coordinates of the rectangle to process for later use. Doesn't actually do any thresholding.

Definition at line 123 of file thresholder.cpp.

123 {
124 rect_left_ = left;
125 rect_top_ = top;
126 rect_width_ = width;
127 rect_height_ = height;
128}

◆ SetSourceYResolution()

void tesseract::ImageThresholder::SetSourceYResolution ( int  ppi)
inline

Definition at line 85 of file thresholder.h.

85 {
86 yres_ = ppi;
87 estimated_res_ = ppi;
88 }

◆ ThresholdRectToPix()

void tesseract::ImageThresholder::ThresholdRectToPix ( Pix *  src_pix,
int  num_channels,
const int *  thresholds,
const int *  hi_values,
Pix **  pix 
) const
protected

Threshold the rectangle, taking everything except the src_pix from the class, using thresholds/hi_values to the output pix. NOTE that num_channels is the size of the thresholds and hi_values

Definition at line 296 of file thresholder.cpp.

300 {
301 *pix = pixCreate(rect_width_, rect_height_, 1);
302 uint32_t* pixdata = pixGetData(*pix);
303 int wpl = pixGetWpl(*pix);
304 int src_wpl = pixGetWpl(src_pix);
305 uint32_t* srcdata = pixGetData(src_pix);
306 pixSetXRes(*pix, pixGetXRes(src_pix));
307 pixSetYRes(*pix, pixGetYRes(src_pix));
308 for (int y = 0; y < rect_height_; ++y) {
309 const uint32_t* linedata = srcdata + (y + rect_top_) * src_wpl;
310 uint32_t* pixline = pixdata + y * wpl;
311 for (int x = 0; x < rect_width_; ++x) {
312 bool white_result = true;
313 for (int ch = 0; ch < num_channels; ++ch) {
314 int pixel =
315 GET_DATA_BYTE(linedata, (x + rect_left_) * num_channels + ch);
316 if (hi_values[ch] >= 0 &&
317 (pixel > thresholds[ch]) == (hi_values[ch] == 0)) {
318 white_result = false;
319 break;
320 }
321 }
322 if (white_result)
323 CLEAR_DATA_BIT(pixline, x);
324 else
325 SET_DATA_BIT(pixline, x);
326 }
327 }
328}

◆ ThresholdToPix()

bool tesseract::ImageThresholder::ThresholdToPix ( PageSegMode  pageseg_mode,
Pix **  pix 
)
virtual

Returns false on error.

Threshold the source image as efficiently as possible to the output Pix. Creates a Pix and sets pix to point to the resulting pointer. Caller must use pixDestroy to free the created Pix. Returns false on error.

Definition at line 185 of file thresholder.cpp.

185 {
186 if (image_width_ > INT16_MAX || image_height_ > INT16_MAX) {
187 tprintf("Image too large: (%d, %d)\n", image_width_, image_height_);
188 return false;
189 }
190 if (pix_channels_ == 0) {
191 // We have a binary image, but it still has to be copied, as this API
192 // allows the caller to modify the output.
193 Pix* original = GetPixRect();
194 *pix = pixCopy(nullptr, original);
195 pixDestroy(&original);
196 } else {
198 }
199 return true;
200}
void OtsuThresholdRectToPix(Pix *src_pix, Pix **out_pix) const

Member Data Documentation

◆ estimated_res_

int tesseract::ImageThresholder::estimated_res_
protected

Resolution estimate from text size.

Definition at line 180 of file thresholder.h.

◆ image_height_

int tesseract::ImageThresholder::image_height_
protected

Height of source pix_.

Definition at line 174 of file thresholder.h.

◆ image_width_

int tesseract::ImageThresholder::image_width_
protected

Width of source pix_.

Definition at line 173 of file thresholder.h.

◆ pix_

Pix* tesseract::ImageThresholder::pix_
protected

Clone or other copy of the source Pix. The pix will always be PixDestroy()ed on destruction of the class.

Definition at line 171 of file thresholder.h.

◆ pix_channels_

int tesseract::ImageThresholder::pix_channels_
protected

Number of 8-bit channels in pix_.

Definition at line 175 of file thresholder.h.

◆ pix_wpl_

int tesseract::ImageThresholder::pix_wpl_
protected

Words per line of pix_.

Definition at line 176 of file thresholder.h.

◆ rect_height_

int tesseract::ImageThresholder::rect_height_
protected

Definition at line 184 of file thresholder.h.

◆ rect_left_

int tesseract::ImageThresholder::rect_left_
protected

Definition at line 181 of file thresholder.h.

◆ rect_top_

int tesseract::ImageThresholder::rect_top_
protected

Definition at line 182 of file thresholder.h.

◆ rect_width_

int tesseract::ImageThresholder::rect_width_
protected

Definition at line 183 of file thresholder.h.

◆ scale_

int tesseract::ImageThresholder::scale_
protected

Scale factor from original image.

Definition at line 178 of file thresholder.h.

◆ yres_

int tesseract::ImageThresholder::yres_
protected

y pixels/inch in source image.

Definition at line 179 of file thresholder.h.


The documentation for this class was generated from the following files: