1 // Three-lobed Lanczos, the most common choice.
2 // Note that if you change this, the accuracy for LANCZOS_TABLE_SIZE
3 // needs to be recomputed.
4 #define LANCZOS_RADIUS 3.0f
13 #include <Eigen/Sparse>
14 #include <Eigen/SparseQR>
15 #include <Eigen/OrderingMethods>
17 #include "effect_chain.h"
18 #include "effect_util.h"
21 #include "resample_effect.h"
24 using namespace Eigen;
34 return 1.0f - fabs(x);
40 float lanczos_weight(float x)
42 if (fabs(x) > LANCZOS_RADIUS) {
45 return sinc(M_PI * x) * sinc((M_PI / LANCZOS_RADIUS) * x);
49 // The weight function can be expensive to compute over and over again
50 // (which will happen during e.g. a zoom), but it is also easy to interpolate
51 // linearly. We compute the right half of the function (in the range of
52 // 0..LANCZOS_RADIUS), with two guard elements for easier interpolation, and
53 // linearly interpolate to get our function.
55 // We want to scale the table so that the maximum error is always smaller
56 // than 1e-6. As per http://www-solar.mcs.st-andrews.ac.uk/~clare/Lectures/num-analysis/Numan_chap3.pdf,
57 // the error for interpolating a function linearly between points [a,b] is
59 // e = 1/2 (x-a)(x-b) f''(u_x)
61 // for some point u_x in [a,b] (where f(x) is our Lanczos function; we're
62 // assuming LANCZOS_RADIUS=3 from here on). Obviously this is bounded by
63 // f''(x) over the entire range. Numeric optimization shows the maximum of
64 // |f''(x)| to be in x=1.09369819474562880, with the value 2.40067758733152381.
65 // So if the steps between consecutive values are called d, we get
67 // |e| <= 1/2 (d/2)^2 2.4007
70 // Solve for e = 1e-6 yields a step size of 0.0027, which to cover the range
71 // 0..3 needs 1109 steps. We round up to the next power of two, just to be sure.
73 // You need to call lanczos_table_init_done before the first call to
74 // lanczos_weight_cached.
75 #define LANCZOS_TABLE_SIZE 2048
76 static once_flag lanczos_table_init_done;
77 float lanczos_table[LANCZOS_TABLE_SIZE + 2];
79 void init_lanczos_table()
81 for (unsigned i = 0; i < LANCZOS_TABLE_SIZE + 2; ++i) {
82 lanczos_table[i] = lanczos_weight(float(i) * (LANCZOS_RADIUS / LANCZOS_TABLE_SIZE));
86 float lanczos_weight_cached(float x)
89 if (x > LANCZOS_RADIUS) {
92 float table_pos = x * (LANCZOS_TABLE_SIZE / LANCZOS_RADIUS);
93 unsigned table_pos_int = int(table_pos); // Truncate towards zero.
94 float table_pos_frac = table_pos - table_pos_int;
95 assert(table_pos < LANCZOS_TABLE_SIZE + 2);
96 return lanczos_table[table_pos_int] +
97 table_pos_frac * (lanczos_table[table_pos_int + 1] - lanczos_table[table_pos_int]);
100 // Euclid's algorithm, from Wikipedia.
101 unsigned gcd(unsigned a, unsigned b)
111 template<class DestFloat>
112 unsigned combine_samples(const Tap<float> *src, Tap<DestFloat> *dst, float num_subtexels, float inv_num_subtexels, unsigned num_src_samples, unsigned max_samples_saved, float pos1_pos2_diff, float inv_pos1_pos2_diff)
114 // Cut off near-zero values at both sides.
115 unsigned num_samples_saved = 0;
116 while (num_samples_saved < max_samples_saved &&
117 num_src_samples > 0 &&
118 fabs(src[0].weight) < 1e-6) {
123 while (num_samples_saved < max_samples_saved &&
124 num_src_samples > 0 &&
125 fabs(src[num_src_samples - 1].weight) < 1e-6) {
130 for (unsigned i = 0, j = 0; i < num_src_samples; ++i, ++j) {
131 // Copy the sample directly; it will be overwritten later if we can combine.
132 if (dst != nullptr) {
133 dst[j].weight = convert_float<float, DestFloat>(src[i].weight);
134 dst[j].pos = convert_float<float, DestFloat>(src[i].pos);
137 if (i == num_src_samples - 1) {
138 // Last sample; cannot combine.
141 assert(num_samples_saved <= max_samples_saved);
142 if (num_samples_saved == max_samples_saved) {
143 // We could maybe save more here, but other rows can't, so don't bother.
147 float w1 = src[i].weight;
148 float w2 = src[i + 1].weight;
149 if (w1 * w2 < 0.0f) {
150 // Differing signs; cannot combine.
154 float pos1 = src[i].pos;
155 float pos2 = src[i + 1].pos;
158 DestFloat pos, total_weight;
160 combine_two_samples(w1, w2, pos1, pos1_pos2_diff, inv_pos1_pos2_diff, num_subtexels, inv_num_subtexels, &pos, &total_weight, &sum_sq_error);
162 // If the interpolation error is larger than that of about sqrt(2) of
163 // a level at 8-bit precision, don't combine. (You'd think 1.0 was enough,
164 // but since the artifacts are not really random, they can get quite
165 // visible. On the other hand, going to 0.25f, I can see no change at
166 // all with 8-bit output, so it would not seem to be worth it.)
167 if (sum_sq_error > 0.5f / (255.0f * 255.0f)) {
171 // OK, we can combine this and the next sample.
172 if (dst != nullptr) {
173 dst[j].weight = total_weight;
177 ++i; // Skip the next sample.
180 return num_samples_saved;
183 // Normalize so that the sum becomes one. Note that we do it twice;
184 // this sometimes helps a tiny little bit when we have many samples.
186 void normalize_sum(Tap<T>* vals, unsigned num)
188 for (int normalize_pass = 0; normalize_pass < 2; ++normalize_pass) {
190 for (unsigned i = 0; i < num; ++i) {
191 sum += to_fp32(vals[i].weight);
193 float inv_sum = 1.0 / sum;
194 for (unsigned i = 0; i < num; ++i) {
195 vals[i].weight = from_fp32<T>(to_fp32(vals[i].weight) * inv_sum);
200 // Make use of the bilinear filtering in the GPU to reduce the number of samples
201 // we need to make. This is a bit more complex than BlurEffect since we cannot combine
202 // two neighboring samples if their weights have differing signs, so we first need to
203 // figure out the maximum number of samples. Then, we downconvert all the weights to
204 // that number -- we could have gone for a variable-length system, but this is simpler,
205 // and the gains would probably be offset by the extra cost of checking when to stop.
207 // The greedy strategy for combining samples is optimal.
208 template<class DestFloat>
209 unsigned combine_many_samples(const Tap<float> *weights, unsigned src_size, unsigned src_samples, unsigned dst_samples, unique_ptr<Tap<DestFloat>[]> *bilinear_weights)
211 float num_subtexels = src_size / movit_texel_subpixel_precision;
212 float inv_num_subtexels = movit_texel_subpixel_precision / src_size;
213 float pos1_pos2_diff = 1.0f / src_size;
214 float inv_pos1_pos2_diff = src_size;
216 unsigned max_samples_saved = UINT_MAX;
217 for (unsigned y = 0; y < dst_samples && max_samples_saved > 0; ++y) {
218 unsigned num_samples_saved = combine_samples<DestFloat>(weights + y * src_samples, nullptr, num_subtexels, inv_num_subtexels, src_samples, max_samples_saved, pos1_pos2_diff, inv_pos1_pos2_diff);
219 max_samples_saved = min(max_samples_saved, num_samples_saved);
222 // Now that we know the right width, actually combine the samples.
223 unsigned src_bilinear_samples = src_samples - max_samples_saved;
224 bilinear_weights->reset(new Tap<DestFloat>[dst_samples * src_bilinear_samples]);
225 for (unsigned y = 0; y < dst_samples; ++y) {
226 Tap<DestFloat> *bilinear_weights_ptr = bilinear_weights->get() + y * src_bilinear_samples;
227 unsigned num_samples_saved = combine_samples(
228 weights + y * src_samples,
229 bilinear_weights_ptr,
236 assert(num_samples_saved == max_samples_saved);
237 normalize_sum(bilinear_weights_ptr, src_bilinear_samples);
239 return src_bilinear_samples;
242 // Compute the sum of squared errors between the ideal weights (which are
243 // assumed to fall exactly on pixel centers) and the weights that result
244 // from sampling at <bilinear_weights>. The primary reason for the difference
245 // is inaccuracy in the sampling positions, both due to limited precision
246 // in storing them (already inherent in sending them in as fp16_int_t)
247 // and in subtexel sampling precision (which we calculate in this function).
249 double compute_sum_sq_error(const Tap<float>* weights, unsigned num_weights,
250 const Tap<T>* bilinear_weights, unsigned num_bilinear_weights,
253 // Find the effective range of the bilinear-optimized kernel.
254 // Due to rounding of the positions, this is not necessarily the same
255 // as the intended range (ie., the range of the original weights).
256 int lower_pos = int(floor(to_fp32(bilinear_weights[0].pos) * size - 0.5f));
257 int upper_pos = int(ceil(to_fp32(bilinear_weights[num_bilinear_weights - 1].pos) * size - 0.5f)) + 2;
258 lower_pos = min<int>(lower_pos, lrintf(weights[0].pos * size - 0.5f));
259 upper_pos = max<int>(upper_pos, lrintf(weights[num_weights - 1].pos * size - 0.5f) + 1);
261 float* effective_weights = new float[upper_pos - lower_pos];
262 for (int i = 0; i < upper_pos - lower_pos; ++i) {
263 effective_weights[i] = 0.0f;
266 // Now find the effective weights that result from this sampling.
267 for (unsigned i = 0; i < num_bilinear_weights; ++i) {
268 const float pixel_pos = to_fp32(bilinear_weights[i].pos) * size - 0.5f;
269 const int x0 = int(floor(pixel_pos)) - lower_pos;
270 const int x1 = x0 + 1;
271 const float f = lrintf((pixel_pos - (x0 + lower_pos)) / movit_texel_subpixel_precision) * movit_texel_subpixel_precision;
275 assert(x0 < upper_pos - lower_pos);
276 assert(x1 < upper_pos - lower_pos);
278 effective_weights[x0] += to_fp32(bilinear_weights[i].weight) * (1.0f - f);
279 effective_weights[x1] += to_fp32(bilinear_weights[i].weight) * f;
282 // Subtract the desired weights to get the error.
283 for (unsigned i = 0; i < num_weights; ++i) {
284 const int x = lrintf(weights[i].pos * size - 0.5f) - lower_pos;
286 assert(x < upper_pos - lower_pos);
288 effective_weights[x] -= weights[i].weight;
291 double sum_sq_error = 0.0;
292 for (unsigned i = 0; i < num_weights; ++i) {
293 sum_sq_error += effective_weights[i] * effective_weights[i];
296 delete[] effective_weights;
302 ResampleEffect::ResampleEffect()
305 offset_x(0.0f), offset_y(0.0f),
306 zoom_x(1.0f), zoom_y(1.0f),
307 zoom_center_x(0.5f), zoom_center_y(0.5f)
309 register_int("width", &output_width);
310 register_int("height", &output_height);
312 // The first blur pass will forward resolution information to us.
313 hpass_owner.reset(new SingleResamplePassEffect(this));
314 hpass = hpass_owner.get();
315 CHECK(hpass->set_int("direction", SingleResamplePassEffect::HORIZONTAL));
316 vpass_owner.reset(new SingleResamplePassEffect(this));
317 vpass = vpass_owner.get();
318 CHECK(vpass->set_int("direction", SingleResamplePassEffect::VERTICAL));
323 ResampleEffect::~ResampleEffect()
327 void ResampleEffect::rewrite_graph(EffectChain *graph, Node *self)
329 Node *hpass_node = graph->add_node(hpass_owner.release());
330 Node *vpass_node = graph->add_node(vpass_owner.release());
331 graph->connect_nodes(hpass_node, vpass_node);
332 graph->replace_receiver(self, hpass_node);
333 graph->replace_sender(self, vpass_node);
334 self->disabled = true;
337 // We get this information forwarded from the first blur pass,
338 // since we are not part of the chain ourselves.
339 void ResampleEffect::inform_input_size(unsigned input_num, unsigned width, unsigned height)
341 assert(input_num == 0);
345 input_height = height;
349 void ResampleEffect::update_size()
352 ok |= hpass->set_int("input_width", input_width);
353 ok |= hpass->set_int("input_height", input_height);
354 ok |= hpass->set_int("output_width", output_width);
355 ok |= hpass->set_int("output_height", input_height);
357 ok |= vpass->set_int("input_width", output_width);
358 ok |= vpass->set_int("input_height", input_height);
359 ok |= vpass->set_int("output_width", output_width);
360 ok |= vpass->set_int("output_height", output_height);
364 // The offset added due to zoom may have changed with the size.
365 update_offset_and_zoom();
368 void ResampleEffect::update_offset_and_zoom()
372 // Zoom from the right origin. (zoom_center is given in normalized coordinates,
374 float extra_offset_x = zoom_center_x * (1.0f - 1.0f / zoom_x) * input_width;
375 float extra_offset_y = (1.0f - zoom_center_y) * (1.0f - 1.0f / zoom_y) * input_height;
377 ok |= hpass->set_float("offset", extra_offset_x + offset_x);
378 ok |= vpass->set_float("offset", extra_offset_y - offset_y); // Compensate for the bottom-left origin.
379 ok |= hpass->set_float("zoom", zoom_x);
380 ok |= vpass->set_float("zoom", zoom_y);
385 bool ResampleEffect::set_float(const string &key, float value) {
386 if (key == "width") {
387 output_width = value;
391 if (key == "height") {
392 output_height = value;
398 update_offset_and_zoom();
403 update_offset_and_zoom();
406 if (key == "zoom_x") {
411 update_offset_and_zoom();
414 if (key == "zoom_y") {
419 update_offset_and_zoom();
422 if (key == "zoom_center_x") {
423 zoom_center_x = value;
424 update_offset_and_zoom();
427 if (key == "zoom_center_y") {
428 zoom_center_y = value;
429 update_offset_and_zoom();
435 SingleResamplePassEffect::SingleResamplePassEffect(ResampleEffect *parent)
437 direction(HORIZONTAL),
442 last_input_width(-1),
443 last_input_height(-1),
444 last_output_width(-1),
445 last_output_height(-1),
446 last_offset(0.0 / 0.0), // NaN.
447 last_zoom(0.0 / 0.0) // NaN.
449 register_int("direction", (int *)&direction);
450 register_int("input_width", &input_width);
451 register_int("input_height", &input_height);
452 register_int("output_width", &output_width);
453 register_int("output_height", &output_height);
454 register_float("offset", &offset);
455 register_float("zoom", &zoom);
456 register_uniform_sampler2d("sample_tex", &uniform_sample_tex);
457 register_uniform_int("num_samples", &uniform_num_samples);
458 register_uniform_float("num_loops", &uniform_num_loops);
459 register_uniform_float("slice_height", &uniform_slice_height);
460 register_uniform_float("sample_x_scale", &uniform_sample_x_scale);
461 register_uniform_float("sample_x_offset", &uniform_sample_x_offset);
462 register_uniform_float("whole_pixel_offset", &uniform_whole_pixel_offset);
464 call_once(lanczos_table_init_done, init_lanczos_table);
467 SingleResamplePassEffect::~SingleResamplePassEffect()
471 string SingleResamplePassEffect::output_fragment_shader()
474 sprintf(buf, "#define DIRECTION_VERTICAL %d\n", (direction == VERTICAL));
475 return buf + read_file("resample_effect.frag");
478 // Using vertical scaling as an example:
480 // Generally out[y] = w0 * in[yi] + w1 * in[yi + 1] + w2 * in[yi + 2] + ...
482 // Obviously, yi will depend on y (in a not-quite-linear way), but so will
483 // the weights w0, w1, w2, etc.. The easiest way of doing this is to encode,
484 // for each sample, the weight and the yi value, e.g. <yi, w0>, <yi + 1, w1>,
485 // and so on. For each y, we encode these along the x-axis (since that is spare),
486 // so out[0] will read from parameters <x,y> = <0,0>, <1,0>, <2,0> and so on.
488 // For horizontal scaling, we fill in the exact same texture;
489 // the shader just interprets it differently.
490 void SingleResamplePassEffect::update_texture(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num)
492 unsigned src_size, dst_size;
493 if (direction == SingleResamplePassEffect::HORIZONTAL) {
494 assert(input_height == output_height);
495 src_size = input_width;
496 dst_size = output_width;
497 } else if (direction == SingleResamplePassEffect::VERTICAL) {
498 assert(input_width == output_width);
499 src_size = input_height;
500 dst_size = output_height;
505 ScalingWeights weights = calculate_bilinear_scaling_weights(src_size, dst_size, zoom, offset);
506 src_bilinear_samples = weights.src_bilinear_samples;
507 num_loops = weights.num_loops;
508 slice_height = 1.0f / weights.num_loops;
510 // Encode as a two-component texture. Note the GL_REPEAT.
511 glActiveTexture(GL_TEXTURE0 + *sampler_num);
513 glBindTexture(GL_TEXTURE_2D, tex.get_texnum());
516 GLenum type, internal_format;
518 assert((weights.bilinear_weights_fp16 == nullptr) != (weights.bilinear_weights_fp32 == nullptr));
519 if (weights.bilinear_weights_fp32 != nullptr) {
521 internal_format = GL_RG32F;
522 pixels = weights.bilinear_weights_fp32.get();
524 type = GL_HALF_FLOAT;
525 internal_format = GL_RG16F;
526 pixels = weights.bilinear_weights_fp16.get();
529 tex.update(weights.src_bilinear_samples, weights.dst_samples, internal_format, GL_RG, type, pixels);
534 ScalingWeights calculate_scaling_weights(unsigned src_size, unsigned dst_size, float zoom, float offset)
536 // Only needed if run from outside ResampleEffect.
537 call_once(lanczos_table_init_done, init_lanczos_table);
539 // For many resamplings (e.g. 640 -> 1280), we will end up with the same
540 // set of samples over and over again in a loop. Thus, we can compute only
541 // the first such loop, and then ask the card to repeat the texture for us.
542 // This is both easier on the texture cache and lowers our CPU cost for
543 // generating the kernel somewhat.
544 float scaling_factor;
546 if (fabs(zoom - 1.0f) < 1e-6) {
547 num_loops = gcd(src_size, dst_size);
548 scaling_factor = float(dst_size) / float(src_size);
550 // If zooming is enabled (ie., zoom != 1), we turn off the looping.
551 // We _could_ perhaps do it for rational zoom levels (especially
552 // things like 2:1), but it doesn't seem to be worth it, given that
553 // the most common use case would seem to be varying the zoom
554 // from frame to frame.
556 scaling_factor = zoom * float(dst_size) / float(src_size);
558 unsigned dst_samples = dst_size / num_loops;
560 // Sample the kernel in the right place. A diagram with a triangular kernel
561 // (corresponding to linear filtering, and obviously with radius 1)
562 // for easier ASCII art drawing:
568 // x---x---x x x---x---x---x
570 // Scaling up (in this case, 2x) means sampling more densely:
576 // x-x-x-x-x-x x x x-x-x-x-x-x-x-x
578 // When scaling up, any destination pixel will only be influenced by a few
579 // (in this case, two) neighboring pixels, and more importantly, the number
580 // will not be influenced by the scaling factor. (Note, however, that the
581 // pixel centers have moved, due to OpenGL's center-pixel convention.)
582 // The only thing that changes is the weights themselves, as the sampling
583 // points are at different distances from the original pixels.
585 // Scaling down is a different story:
591 // --x------ x --x-------x--
593 // Again, the pixel centers have moved in a maybe unintuitive fashion,
594 // although when you consider that there are multiple source pixels around,
595 // it's not so bad as at first look:
601 // --x-------x-------x-------x--
603 // As you can see, the new pixels become averages of the two neighboring old
604 // ones (the situation for Lanczos is of course more complex).
606 // Anyhow, in this case we clearly need to look at more source pixels
607 // to compute the destination pixel, and how many depend on the scaling factor.
608 // Thus, the kernel width will vary with how much we scale.
609 float radius_scaling_factor = min(scaling_factor, 1.0f);
610 const int int_radius = lrintf(LANCZOS_RADIUS / radius_scaling_factor);
611 const int src_samples = int_radius * 2 + 1;
612 unique_ptr<Tap<float>[]> weights(new Tap<float>[dst_samples * src_samples]);
613 float subpixel_offset = offset - lrintf(offset); // The part not covered by whole_pixel_offset.
614 assert(subpixel_offset >= -0.5f && subpixel_offset <= 0.5f);
615 float inv_scaling_factor = 1.0f / scaling_factor;
616 for (unsigned y = 0; y < dst_samples; ++y) {
617 // Find the point around which we want to sample the source image,
618 // compensating for differing pixel centers as the scale changes.
619 float center_src_y = (y + 0.5f) * inv_scaling_factor - 0.5f;
620 int base_src_y = lrintf(center_src_y);
622 // Now sample <int_radius> pixels on each side around that point.
623 float inv_src_size = 1.0 / float(src_size);
624 for (int i = 0; i < src_samples; ++i) {
625 int src_y = base_src_y + i - int_radius;
626 float weight = lanczos_weight_cached(radius_scaling_factor * (src_y - center_src_y - subpixel_offset));
627 weights[y * src_samples + i].weight = weight * radius_scaling_factor;
628 weights[y * src_samples + i].pos = (src_y + 0.5f) * inv_src_size;
633 ret.src_bilinear_samples = src_samples;
634 ret.dst_samples = dst_samples;
635 ret.num_loops = num_loops;
636 ret.bilinear_weights_fp16 = nullptr;
637 ret.bilinear_weights_fp32 = move(weights);
643 ScalingWeights calculate_bilinear_scaling_weights(unsigned src_size, unsigned dst_size, float zoom, float offset)
645 ScalingWeights ret = calculate_scaling_weights(src_size, dst_size, zoom, offset);
646 unique_ptr<Tap<float>[]> weights = move(ret.bilinear_weights_fp32);
647 const int src_samples = ret.src_bilinear_samples;
649 // Now make use of the bilinear filtering in the GPU to reduce the number of samples
650 // we need to make. Try fp16 first; if it's not accurate enough, we go to fp32.
651 // Our tolerance level for total error is a bit higher than the one for invididual
652 // samples, since one would assume overall errors in the shape don't matter as much.
653 const float max_error = 2.0f / (255.0f * 255.0f);
654 unique_ptr<Tap<fp16_int_t>[]> bilinear_weights_fp16;
655 int src_bilinear_samples = combine_many_samples(weights.get(), src_size, src_samples, ret.dst_samples, &bilinear_weights_fp16);
656 unique_ptr<Tap<float>[]> bilinear_weights_fp32 = nullptr;
657 double max_sum_sq_error_fp16 = 0.0;
658 for (unsigned y = 0; y < ret.dst_samples; ++y) {
659 double sum_sq_error_fp16 = compute_sum_sq_error(
660 weights.get() + y * src_samples, src_samples,
661 bilinear_weights_fp16.get() + y * src_bilinear_samples, src_bilinear_samples,
663 max_sum_sq_error_fp16 = std::max(max_sum_sq_error_fp16, sum_sq_error_fp16);
664 if (max_sum_sq_error_fp16 > max_error) {
669 if (max_sum_sq_error_fp16 > max_error) {
670 bilinear_weights_fp16.reset();
671 src_bilinear_samples = combine_many_samples(weights.get(), src_size, src_samples, ret.dst_samples, &bilinear_weights_fp32);
674 ret.src_bilinear_samples = src_bilinear_samples;
675 ret.bilinear_weights_fp16 = move(bilinear_weights_fp16);
676 ret.bilinear_weights_fp32 = move(bilinear_weights_fp32);
680 void SingleResamplePassEffect::set_gl_state(GLuint glsl_program_num, const string &prefix, unsigned *sampler_num)
682 Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
684 assert(input_width > 0);
685 assert(input_height > 0);
686 assert(output_width > 0);
687 assert(output_height > 0);
689 if (input_width != last_input_width ||
690 input_height != last_input_height ||
691 output_width != last_output_width ||
692 output_height != last_output_height ||
693 offset != last_offset ||
695 update_texture(glsl_program_num, prefix, sampler_num);
696 last_input_width = input_width;
697 last_input_height = input_height;
698 last_output_width = output_width;
699 last_output_height = output_height;
700 last_offset = offset;
704 glActiveTexture(GL_TEXTURE0 + *sampler_num);
706 glBindTexture(GL_TEXTURE_2D, tex.get_texnum());
709 uniform_sample_tex = *sampler_num;
711 uniform_num_samples = src_bilinear_samples;
712 uniform_num_loops = num_loops;
713 uniform_slice_height = slice_height;
715 // Instructions for how to convert integer sample numbers to positions in the weight texture.
716 uniform_sample_x_scale = 1.0f / src_bilinear_samples;
717 uniform_sample_x_offset = 0.5f / src_bilinear_samples;
719 if (direction == SingleResamplePassEffect::VERTICAL) {
720 uniform_whole_pixel_offset = lrintf(offset) / float(input_height);
722 uniform_whole_pixel_offset = lrintf(offset) / float(input_width);
726 Support2DTexture::Support2DTexture()
728 glGenTextures(1, &texnum);
730 glBindTexture(GL_TEXTURE_2D, texnum);
732 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
734 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
736 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
740 Support2DTexture::~Support2DTexture()
742 glDeleteTextures(1, &texnum);
746 void Support2DTexture::update(GLint width, GLint height, GLenum internal_format, GLenum format, GLenum type, const GLvoid * data)
748 glBindTexture(GL_TEXTURE_2D, texnum);
750 if (width == last_texture_width &&
751 height == last_texture_height &&
752 internal_format == last_texture_internal_format) {
753 // Texture dimensions and type are unchanged; it is more efficient
754 // to just update it rather than making an entirely new texture.
755 glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, height, format, type, data);
758 glTexImage2D(GL_TEXTURE_2D, 0, internal_format, width, height, 0, format, type, data);
760 last_texture_width = width;
761 last_texture_height = height;
762 last_texture_internal_format = internal_format;