Differential D25645 Diff 71076 kstars/fitsviewer/stretch.cpp

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kstars/fitsviewer/stretch.cpp

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11#include "stretch.h" 11​#include "stretch.h"
12 12​
13#include <fitsio.h> 13​#include <fitsio.h>
14#include <math.h> 14​#include <math.h>
15#include <QtConcurrent> 15​#include <QtConcurrent>
16 16​
17namespace { 17​namespace {
18 18​
19// Returns the median v of the vector. 19​// Returns the median value of the vector.
20// The vector is modified in an undefined way. 20​// The vector is modified in an undefined way.
21template <typename T> 21​template <typename T>
22T median(std::vector<T>& values) 22​T median(std::vector<T>& values)
23{ 23​{
24 const int middle = values.size() / 2; 24​ const int middle = values.size() / 2;
25 std::nth_element(values.begin(), values.begin() + middle, values.end()); 25​ std::nth_element(values.begin(), values.begin() + middle, values.end());
26 return values[middle]; 26​ return values[middle];
27} 27​}
28 28​
29​// Returns the rough max of the buffer.
30​template <typename T>
31​T sampledMax(T *values, int size, int sampleBy)
32​{
33​ T maxVal = 0;
34​ for (int i = 0; i < size; i+= sampleBy)
35​ if (maxVal < values[i])
36​ maxVal = values[i];
37​ return maxVal;
38​}
39​
29// Returns the median of the sample values. 40​// Returns the median of the sample values.
30// The values are not modified. 41​// The values are not modified.
31template <typename T> 42​template <typename T>
32T median(T *values, int size, int sampleBy) 43​T median(T *values, int size, int sampleBy)
33{ 44​{
34 const int downsampled_size = size / sampleBy; 45​ const int downsampled_size = size / sampleBy;
35 std::vector<T> samples(downsampled_size); 46​ std::vector<T> samples(downsampled_size);
36 for (int index = 0, i = 0; i < downsampled_size; ++i, index += sampleBy) 47​ for (int index = 0, i = 0; i < downsampled_size; ++i, index += sampleBy)
37 samples[i] = values[index]; 48​ samples[i] = values[index];
38 return median(samples); 49​ return median(samples);
39} 50​}
40 51​
41// This stretches one channel given the input parameters. 52​// This stretches one channel given the input parameters.
42// Based on the spec in section 8.5.6 53​// Based on the spec in section 8.5.6
43// http://pixinsight.com/doc/docs/XISF-1.0-spec/XISF-1.0-spec.html 54​// http://pixinsight.com/doc/docs/XISF-1.0-spec/XISF-1.0-spec.html
44// Uses multiple threads, blocks until done. 55​// Uses multiple threads, blocks until done.
45// The extension parameters are not used. 56​// The extension parameters are not used.
57​// Sampling is applied to the output (that is, with sampling=2, we compute every other output
58​// sample both in width and height, so the output would have about 4X fewer pixels.
46template <typename T> 59​template <typename T>
47void stretchOneChannel(T *input_buffer, QImage *output_image, 60​void stretchOneChannel(T *input_buffer, QImage *output_image,
48 const StretchParams& stretch_params, 61​ const StretchParams& stretch_params,
49 int input_range, int image_height, int image_width) 62​ int input_range, int image_height, int image_width, int sampling)
50{ 63​{
51 QVector<QFuture<void>> futures; 64​ QVector<QFuture<void>> futures;
52 65​
53 // We're outputting uint8, so the max output is 255. 66​ // We're outputting uint8, so the max output is 255.
54 constexpr int maxOutput = 255; 67​ constexpr int maxOutput = 255;
55 68​
56 // Maximum possible input value (e.g. 1024*64 - 1 for a 16 bit unsigned int). 69​ // Maximum possible input value (e.g. 1024*64 - 1 for a 16 bit unsigned int).
57 const float maxInput = input_range > 1 ? input_range - 1 : input_range; 70​ const float maxInput = input_range > 1 ? input_range - 1 : input_range;
58 71​
59 const float midtones = stretch_params.grey_red.midtones; 72​ const float midtones = stretch_params.grey_red.midtones;
60 const float highlights = stretch_params.grey_red.highlights; 73​ const float highlights = stretch_params.grey_red.highlights;
61 const float shadows = stretch_params.grey_red.shadows; 74​ const float shadows = stretch_params.grey_red.shadows;
62 75​
63 // Precomputed expressions moved out of the loop. 76​ // Precomputed expressions moved out of the loop.
64 // hightlights - shadows, protecting for divide-by-0, in a 0->1.0 scale. 77​ // hightlights - shadows, protecting for divide-by-0, in a 0->1.0 scale.
65 const float hsRangeFactor = highlights == shadows ? 1.0 : 1.0 / (highlights - shadows); 78​ const float hsRangeFactor = highlights == shadows ? 1.0f : 1.0f / (highlights - shadows);
66 // Shadow and highlight values translated to the ADU scale. 79​ // Shadow and highlight values translated to the ADU scale.
67 const T nativeShadows = shadows * maxInput; 80​ const T nativeShadows = shadows * maxInput;
68 const T nativeHighlights = highlights * maxInput; 81​ const T nativeHighlights = highlights * maxInput;
69 // Constants based on above needed for the stretch calculations. 82​ // Constants based on above needed for the stretch calculations.
70 const float k1 = (midtones - 1) * hsRangeFactor * maxOutput / maxInput; 83​ const float k1 = (midtones - 1) * hsRangeFactor * maxOutput / maxInput;
71 const float k2 = ((2 * midtones) - 1) * hsRangeFactor / maxInput; 84​ const float k2 = ((2 * midtones) - 1) * hsRangeFactor / maxInput;
72 85​
73 for (int j = 0; j < image_height; j++) 86​ // Increment the input index by the sampling, the output index increments by 1.
87​ for (int j = 0, jout = 0; j < image_height; j+=sampling, jout++)
74 { 88​ {
75 futures.append(QtConcurrent::run([ = ]() 89​ futures.append(QtConcurrent::run([ = ]()
76 { 90​ {
77 T * inputLine = input_buffer + j * image_width; 91​ T * inputLine = input_buffer + j * image_width;
78 auto * scanLine = output_image->scanLine(j); 92​ auto * scanLine = output_image->scanLine(jout);
79 93​
80 for (int i = 0; i < image_width; i++) 94​ for (int i = 0, iout = 0; i < image_width; i+=sampling, iout++)
81 { 95​ {
82 const T input = inputLine[i]; 96​ const T input = inputLine[i];
83 if (input < nativeShadows) scanLine[i] = 0; 97​ if (input < nativeShadows) scanLine[iout] = 0;
84 else if (input >= nativeHighlights) scanLine[i] = maxOutput; 98​ else if (input >= nativeHighlights) scanLine[iout] = maxOutput;
85 else 99​ else
86 { 100​ {
87 const T inputFloored = (input - nativeShadows); 101​ const T inputFloored = (input - nativeShadows);
88 scanLine[i] = (inputFloored * k1) / (inputFloored * k2 - midtones); 102​ scanLine[iout] = (inputFloored * k1) / (inputFloored * k2 - midtones);
89 } 103​ }
90 } 104​ }
91 })); 105​ }));
92 } 106​ }
93 for(QFuture<void> future : futures) 107​ for(QFuture<void> future : futures)
94 future.waitForFinished(); 108​ future.waitForFinished();
95} 109​}
96 110​
97// This is like the above 1-channel stretch, but extended for 3 channels. 111​// This is like the above 1-channel stretch, but extended for 3 channels.
98// This could have been more modular, but the three channels are combined 112​// This could have been more modular, but the three channels are combined
99// into a single qRgb value at the end, so it seems the simplest thing is to 113​// into a single qRgb value at the end, so it seems the simplest thing is to
100// replicate the code. It is assume the colors are not interleaved--the red image 114​// replicate the code. It is assume the colors are not interleaved--the red image
101// is stored fully, then the green, then the blue. 115​// is stored fully, then the green, then the blue.
116​// Sampling is applied to the output (that is, with sampling=2, we compute every other output
117​// sample both in width and height, so the output would have about 4X fewer pixels.
102template <typename T> 118​template <typename T>
103void stretchThreeChannels(T *inputBuffer, QImage *outputImage, 119​void stretchThreeChannels(T *inputBuffer, QImage *outputImage,
104 const StretchParams& stretchParams, 120​ const StretchParams& stretchParams,
105 int inputRange, int imageHeight, int imageWidth) 121​ int inputRange, int imageHeight, int imageWidth, int sampling)
106{ 122​{
107 QVector<QFuture<void>> futures; 123​ QVector<QFuture<void>> futures;
108 124​
109 // We're outputting uint8, so the max output is 255. 125​ // We're outputting uint8, so the max output is 255.
110 constexpr int maxOutput = 255; 126​ constexpr int maxOutput = 255;
111 127​
112 // Maximum possible input value (e.g. 1024*64 - 1 for a 16 bit unsigned int). 128​ // Maximum possible input value (e.g. 1024*64 - 1 for a 16 bit unsigned int).
113 const float maxInput = inputRange > 1 ? inputRange - 1 : inputRange; 129​ const float maxInput = inputRange > 1 ? inputRange - 1 : inputRange;
114 130​
115 const float midtonesR = stretchParams.grey_red.midtones; 131​ const float midtonesR = stretchParams.grey_red.midtones;
116 const float highlightsR = stretchParams.grey_red.highlights; 132​ const float highlightsR = stretchParams.grey_red.highlights;
117 const float shadowsR = stretchParams.grey_red.shadows; 133​ const float shadowsR = stretchParams.grey_red.shadows;
118 const float midtonesG = stretchParams.green.midtones; 134​ const float midtonesG = stretchParams.green.midtones;
119 const float highlightsG = stretchParams.green.highlights; 135​ const float highlightsG = stretchParams.green.highlights;
120 const float shadowsG = stretchParams.green.shadows; 136​ const float shadowsG = stretchParams.green.shadows;
121 const float midtonesB = stretchParams.blue.midtones; 137​ const float midtonesB = stretchParams.blue.midtones;
122 const float highlightsB = stretchParams.blue.highlights; 138​ const float highlightsB = stretchParams.blue.highlights;
123 const float shadowsB = stretchParams.blue.shadows; 139​ const float shadowsB = stretchParams.blue.shadows;
124 140​
125 // Precomputed expressions moved out of the loop. 141​ // Precomputed expressions moved out of the loop.
126 // hightlights - shadows, protecting for divide-by-0, in a 0->1.0 scale. 142​ // hightlights - shadows, protecting for divide-by-0, in a 0->1.0 scale.
127 const float hsRangeFactorR = highlightsR == shadowsR ? 1.0 : 1.0 / (highlightsR - shadowsR); 143​ const float hsRangeFactorR = highlightsR == shadowsR ? 1.0f : 1.0f / (highlightsR - shadowsR);
128 const float hsRangeFactorG = highlightsG == shadowsG ? 1.0 : 1.0 / (highlightsG - shadowsG); 144​ const float hsRangeFactorG = highlightsG == shadowsG ? 1.0f : 1.0f / (highlightsG - shadowsG);
129 const float hsRangeFactorB = highlightsB == shadowsB ? 1.0 : 1.0 / (highlightsB - shadowsB); 145​ const float hsRangeFactorB = highlightsB == shadowsB ? 1.0f : 1.0f / (highlightsB - shadowsB);
130 // Shadow and highlight values translated to the ADU scale. 146​ // Shadow and highlight values translated to the ADU scale.
131 const T nativeShadowsR = shadowsR * maxInput; 147​ const T nativeShadowsR = shadowsR * maxInput;
132 const T nativeShadowsG = shadowsG * maxInput; 148​ const T nativeShadowsG = shadowsG * maxInput;
133 const T nativeShadowsB = shadowsB * maxInput; 149​ const T nativeShadowsB = shadowsB * maxInput;
134 const T nativeHighlightsR = highlightsR * maxInput; 150​ const T nativeHighlightsR = highlightsR * maxInput;
135 const T nativeHighlightsG = highlightsG * maxInput; 151​ const T nativeHighlightsG = highlightsG * maxInput;
136 const T nativeHighlightsB = highlightsB * maxInput; 152​ const T nativeHighlightsB = highlightsB * maxInput;
137 // Constants based on above needed for the stretch calculations. 153​ // Constants based on above needed for the stretch calculations.
138 const float k1R = (midtonesR - 1) * hsRangeFactorR * maxOutput / maxInput; 154​ const float k1R = (midtonesR - 1) * hsRangeFactorR * maxOutput / maxInput;
139 const float k1G = (midtonesG - 1) * hsRangeFactorG * maxOutput / maxInput; 155​ const float k1G = (midtonesG - 1) * hsRangeFactorG * maxOutput / maxInput;
140 const float k1B = (midtonesB - 1) * hsRangeFactorB * maxOutput / maxInput; 156​ const float k1B = (midtonesB - 1) * hsRangeFactorB * maxOutput / maxInput;
141 const float k2R = ((2 * midtonesR) - 1) * hsRangeFactorR / maxInput; 157​ const float k2R = ((2 * midtonesR) - 1) * hsRangeFactorR / maxInput;
142 const float k2G = ((2 * midtonesG) - 1) * hsRangeFactorG / maxInput; 158​ const float k2G = ((2 * midtonesG) - 1) * hsRangeFactorG / maxInput;
143 const float k2B = ((2 * midtonesB) - 1) * hsRangeFactorB / maxInput; 159​ const float k2B = ((2 * midtonesB) - 1) * hsRangeFactorB / maxInput;
144 160​
145 const int size = imageWidth * imageHeight; 161​ const int size = imageWidth * imageHeight;
146 162​
147 for (int j = 0; j < imageHeight; j++) 163​ for (int j = 0, jout = 0; j < imageHeight; j+=sampling, jout++)
148 { 164​ {
149 futures.append(QtConcurrent::run([ = ]() 165​ futures.append(QtConcurrent::run([ = ]()
150 { 166​ {
151 // R, G, B input images are stored one after another. 167​ // R, G, B input images are stored one after another.
152 T * inputLineR = inputBuffer + j * imageWidth; 168​ T * inputLineR = inputBuffer + j * imageWidth;
153 T * inputLineG = inputLineR + size; 169​ T * inputLineG = inputLineR + size;
154 T * inputLineB = inputLineG + size; 170​ T * inputLineB = inputLineG + size;
155 171​
156 auto * scanLine = reinterpret_cast<QRgb*>(outputImage->scanLine(j)); 172​ auto * scanLine = reinterpret_cast<QRgb*>(outputImage->scanLine(jout));
157 173​
158 for (int i = 0; i < imageWidth; i++) 174​ for (int i = 0, iout = 0; i < imageWidth; i+=sampling, iout++)
159 { 175​ {
160 const T inputR = inputLineR[i]; 176​ const T inputR = inputLineR[i];
161 const T inputG = inputLineG[i]; 177​ const T inputG = inputLineG[i];
162 const T inputB = inputLineB[i]; 178​ const T inputB = inputLineB[i];
163 179​
164 uint8_t red, green, blue; 180​ uint8_t red, green, blue;
165 181​
166 if (inputR < nativeShadowsR) red = 0; 182​ if (inputR < nativeShadowsR) red = 0;
Show All 14 Lines196 }
181 197​
182 if (inputB < nativeShadowsB) blue = 0; 198​ if (inputB < nativeShadowsB) blue = 0;
183 else if (inputB >= nativeHighlightsB) blue = maxOutput; 199​ else if (inputB >= nativeHighlightsB) blue = maxOutput;
184 else 200​ else
185 { 201​ {
186 const T inputFloored = (inputB - nativeShadowsB); 202​ const T inputFloored = (inputB - nativeShadowsB);
187 blue = (inputFloored * k1B) / (inputFloored * k2B - midtonesB); 203​ blue = (inputFloored * k1B) / (inputFloored * k2B - midtonesB);
188 } 204​ }
189 scanLine[i] = qRgb(red, green, blue); 205​ scanLine[iout] = qRgb(red, green, blue);
190 } 206​ }
191 })); 207​ }));
192 } 208​ }
193 for(QFuture<void> future : futures) 209​ for(QFuture<void> future : futures)
194 future.waitForFinished(); 210​ future.waitForFinished();
195} 211​}
196 212​
197template <typename T> 213​template <typename T>
198void stretchChannels(T *input_buffer, QImage *output_image, 214​void stretchChannels(T *input_buffer, QImage *output_image,
199 const StretchParams& stretch_params, 215​ const StretchParams& stretch_params,
200 int input_range, int image_height, int image_width, int num_channels) 216​ int input_range, int image_height, int image_width, int num_channels, int sampling)
201{ 217​{
202 if (num_channels == 1) 218​ if (num_channels == 1)
203 stretchOneChannel(input_buffer, output_image, stretch_params, input_range, 219​ stretchOneChannel(input_buffer, output_image, stretch_params, input_range,
204 image_height, image_width); 220​ image_height, image_width, sampling);
205 else if (num_channels == 3) 221​ else if (num_channels == 3)
206 stretchThreeChannels(input_buffer, output_image, stretch_params, input_range, 222​ stretchThreeChannels(input_buffer, output_image, stretch_params, input_range,
207 image_height, image_width); 223​ image_height, image_width, sampling);
208} 224​}
209 225​
210// See section 8.5.7 in above link http://pixinsight.com/doc/docs/XISF-1.0-spec/XISF-1.0-spec.html 226​// See section 8.5.7 in above link http://pixinsight.com/doc/docs/XISF-1.0-spec/XISF-1.0-spec.html
211template <typename T> 227​template <typename T>
212void computeParamsOneChannel(T *buffer, StretchParams1Channel *params, 228​void computeParamsOneChannel(T *buffer, StretchParams1Channel *params,
213 int inputRange, int height, int width) 229​ int inputRange, int height, int width)
214{ 230​{
215 // Find the median sample. 231​ // Find the median sample.
216 constexpr int maxSamples = 500000; 232​ constexpr int maxSamples = 500000;
217 const int sampleBy = width * height < maxSamples ? 1 : width * height / maxSamples; 233​ const int sampleBy = width * height < maxSamples ? 1 : width * height / maxSamples;
218 const int size = width * height; ​
219 T medianSample = median(buffer, width * height, sampleBy); ​
220 234​
235​ T medianSample = median(buffer, width * height, sampleBy);
221 // Find the Median deviation: 1.4826 * median of abs(sample[i] - median). 236​ // Find the Median deviation: 1.4826 * median of abs(sample[i] - median).
222 const int numSamples = width * height / sampleBy; 237​ const int numSamples = width * height / sampleBy;
223 std::vector<T> deviations(numSamples); 238​ std::vector<T> deviations(numSamples);
224 for (int index = 0, i = 0; i < numSamples; ++i, index += sampleBy) 239​ for (int index = 0, i = 0; i < numSamples; ++i, index += sampleBy)
225 { 240​ {
226 if (medianSample > buffer[index]) 241​ if (medianSample > buffer[index])
227 deviations[i] = medianSample - buffer[index]; 242​ deviations[i] = medianSample - buffer[index];
228 else 243​ else
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247 if (!upperHalf) { 262​ if (!upperHalf) {
248 X = normalizedMedian - shadows; 263​ X = normalizedMedian - shadows;
249 M = B; 264​ M = B;
250 } else { 265​ } else {
251 X = B; 266​ X = B;
252 M = highlights - normalizedMedian; 267​ M = highlights - normalizedMedian;
253 } 268​ }
254 float midtones; 269​ float midtones;
255 if (X == 0) midtones = 0; 270​ if (X == 0) midtones = 0.0f;
256 else if (X == M) midtones = 0.5; 271​ else if (X == M) midtones = 0.5f;
257 else if (X == 1) midtones = 1.0; 272​ else if (X == 1) midtones = 1.0f;
258 else midtones = ((M - 1) * X) / ((2 * M - 1) * X - M); 273​ else midtones = ((M - 1) * X) / ((2 * M - 1) * X - M);
259 274​
260 // Store the params. 275​ // Store the params.
261 params->shadows = shadows; 276​ params->shadows = shadows;
262 params->highlights = highlights; 277​ params->highlights = highlights;
263 params->midtones = midtones; 278​ params->midtones = midtones;
264 params->shadows_expansion = 0.0; 279​ params->shadows_expansion = 0.0;
265 params->highlights_expansion = 1.0; 280​ params->highlights_expansion = 1.0;
266} 281​}
267 282​
268// Need to know the possible range of input values. 283​// Need to know the possible range of input values.
269// Using the type of the sample and guessing. 284​// Using the type of the sample and guessing.
270// Perhaps we should examine the contents for the file 285​// Perhaps we should examine the contents for the file
271// (e.g. look at maximum value and extrapolate from that). 286​// (e.g. look at maximum value and extrapolate from that).
272int getRange(int data_type) 287​int getRange(int data_type)
273{ 288​{
274 switch (data_type) 289​ switch (data_type)
275 { 290​ {
276 case TBYTE: 291​ case TBYTE:
277 return 256; 292​ return 256;
278 break; ​
279 case TSHORT: 293​ case TSHORT:
280 return 64*1024; 294​ return 64*1024;
281 break; ​
282 case TUSHORT: 295​ case TUSHORT:
283 return 64*1024; 296​ return 64*1024;
284 break; ​
285 case TLONG: 297​ case TLONG:
286 return 64*1024; 298​ return 64*1024;
287 break; ​
288 case TFLOAT: 299​ case TFLOAT:
289 return 64*1024; 300​ return 64*1024;
290 break; ​
291 case TLONGLONG: 301​ case TLONGLONG:
292 return 64*1024; 302​ return 64*1024;
293 break; ​
294 case TDOUBLE: 303​ case TDOUBLE:
295 return 64*1024; 304​ return 64*1024;
296 break; ​
297 default: 305​ default:
298 return 64*1024; 306​ return 64*1024;
299 break; ​
300 } 307​ }
301} 308​}
302 309​
303} // namespace 310​} // namespace
304 311​
305Stretch::Stretch(int width, int height, int channels, int data_type) 312​Stretch::Stretch(int width, int height, int channels, int data_type)
306{ 313​{
307 image_width = width; 314​ image_width = width;
308 image_height = height; 315​ image_height = height;
309 image_channels = channels; 316​ image_channels = channels;
310 dataType = data_type; 317​ dataType = data_type;
311 input_range = getRange(dataType); 318​ input_range = getRange(dataType);
312} 319​}
313 320​
314void Stretch::run(uint8_t *input, QImage *outputImage) 321​void Stretch::run(uint8_t *input, QImage *outputImage, int sampling)
315{ 322​{
323​ Q_ASSERT(outputImage->width() == (image_width + sampling - 1) / sampling);
324​ Q_ASSERT(outputImage->height() == (image_height + sampling - 1) / sampling);
325​ recalculateInputRange(input);
326​
316 switch (dataType) 327​ switch (dataType)
317 { 328​ {
318 case TBYTE: 329​ case TBYTE:
319 stretchChannels(reinterpret_cast<uint8_t*>(input), outputImage, params, 330​ stretchChannels(reinterpret_cast<uint8_t*>(input), outputImage, params,
320 input_range, image_height, image_width, image_channels); 331​ input_range, image_height, image_width, image_channels, sampling);
321 break; 332​ break;
322 case TSHORT: 333​ case TSHORT:
323 stretchChannels(reinterpret_cast<short*>(input), outputImage, params, 334​ stretchChannels(reinterpret_cast<short*>(input), outputImage, params,
324 input_range, image_height, image_width, image_channels); 335​ input_range, image_height, image_width, image_channels, sampling);
325 break; 336​ break;
326 case TUSHORT: 337​ case TUSHORT:
327 stretchChannels(reinterpret_cast<unsigned short*>(input), outputImage, params, 338​ stretchChannels(reinterpret_cast<unsigned short*>(input), outputImage, params,
328 input_range, image_height, image_width, image_channels); 339​ input_range, image_height, image_width, image_channels, sampling);
329 break; 340​ break;
330 case TLONG: 341​ case TLONG:
331 stretchChannels(reinterpret_cast<long*>(input), outputImage, params, 342​ stretchChannels(reinterpret_cast<long*>(input), outputImage, params,
332 input_range, image_height, image_width, image_channels); 343​ input_range, image_height, image_width, image_channels, sampling);
333 break; 344​ break;
334 case TFLOAT: 345​ case TFLOAT:
335 stretchChannels(reinterpret_cast<float*>(input), outputImage, params, 346​ stretchChannels(reinterpret_cast<float*>(input), outputImage, params,
336 input_range, image_height, image_width, image_channels); 347​ input_range, image_height, image_width, image_channels, sampling);
337 break; 348​ break;
338 case TLONGLONG: 349​ case TLONGLONG:
339 stretchChannels(reinterpret_cast<long long*>(input), outputImage, params, 350​ stretchChannels(reinterpret_cast<long long*>(input), outputImage, params,
340 input_range, image_height, image_width, image_channels); 351​ input_range, image_height, image_width, image_channels, sampling);
341 break; 352​ break;
342 case TDOUBLE: 353​ case TDOUBLE:
343 stretchChannels(reinterpret_cast<double*>(input), outputImage, params, 354​ stretchChannels(reinterpret_cast<double*>(input), outputImage, params,
344 input_range, image_height, image_width, image_channels); 355​ input_range, image_height, image_width, image_channels, sampling);
345 break; 356​ break;
346 default: 357​ default:
347 break; 358​ break;
348 } 359​ }
349} 360​}
350 361​
362​// The input range for float/double is ambiguous, and we can't tell without the buffer,
363​// so we set it to 64K and possibly reduce it when we see the data.
364​void Stretch::recalculateInputRange(uint8_t *input)
365​{
366​ if (input_range <= 1) return;
367​ if (dataType != TFLOAT && dataType != TDOUBLE) return;
368​
369​ float mx = 0;
370​ if (dataType == TFLOAT)
371​ mx = sampledMax(reinterpret_cast<float*>(input), image_height * image_width, 1000);
372​ else if (dataType == TDOUBLE)
373​ mx = sampledMax(reinterpret_cast<double*>(input), image_height * image_width, 1000);
374​ if (mx <= 1.01f) input_range = 1;
375​}
376​
351StretchParams Stretch::computeParams(uint8_t *input) 377​StretchParams Stretch::computeParams(uint8_t *input)
352{ 378​{
379​ recalculateInputRange(input);
353 StretchParams result; 380​ StretchParams result;
354 for (int channel = 0; channel < image_channels; ++channel) 381​ for (int channel = 0; channel < image_channels; ++channel)
355 { 382​ {
356 int offset = channel * image_width * image_height; 383​ int offset = channel * image_width * image_height;
357 StretchParams1Channel *params = channel == 0 ? &result.grey_red : 384​ StretchParams1Channel *params = channel == 0 ? &result.grey_red :
358 (channel == 1 ? &result.green : &result.blue); 385​ (channel == 1 ? &result.green : &result.blue);
359 switch (dataType) 386​ switch (dataType)
360 { 387​ {
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