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Blur: Improve parallelization
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@ferdnyc
ferdnyc committed Feb 6, 2020
1 parent 7868157 commit fd663c4
Showing 1 changed file with 57 additions and 118 deletions.
175 changes: 57 additions & 118 deletions src/effects/Blur.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -77,154 +77,93 @@ std::shared_ptr<Frame> Blur::GetFrame(std::shared_ptr<Frame> frame, int64_t fram
int w = frame_image->width();
int h = frame_image->height();

// Declare 2-column arrays for each color channel
typedef struct {
unsigned char *red;
unsigned char *green;
unsigned char *blue;
unsigned char *alpha;
} channels;

channels arrays_in {
new unsigned char[w * h](),
new unsigned char[w * h](),
new unsigned char[w * h](),
new unsigned char[w * h]()
};
channels arrays_out {
new unsigned char[w * h](),
new unsigned char[w * h](),
new unsigned char[w * h](),
new unsigned char[w * h]()
};

// Loop through pixels and split RGBA channels into separate arrays
unsigned char *pixels = (unsigned char *) frame_image->bits();

#pragma omp parallel for
for (int pixel = 0; pixel < w * h; ++pixel)
{
// Get the RGBA values from each pixel
arrays_in.red[pixel] = arrays_out.red[pixel] = pixels[pixel * 4];
arrays_in.green[pixel] = arrays_out.green[pixel] = pixels[pixel * 4 + 1];
arrays_in.blue[pixel] = arrays_out.blue[pixel] = pixels[pixel * 4 + 2];
arrays_in.alpha[pixel] = arrays_out.alpha[pixel] = pixels[pixel * 4 + 3];
}

// Initialize target struct pointers for boxBlur operations
channels *array_a = &arrays_in;
channels *array_b = &arrays_out;
// Grab two copies of the image pixel data
QImage image_copy = frame_image->copy();
std::shared_ptr<QImage> frame_image_2 = std::make_shared<QImage>(image_copy);

// Loop through each iteration
for (int iteration = 0; iteration < iteration_value; ++iteration)
{
// HORIZONTAL BLUR (if any)
if (horizontal_radius_value > 0.0) {
// Apply horizontal blur to target RGBA channels
#pragma omp parallel
{
boxBlurH(array_a->red, array_b->red, w, h, horizontal_radius_value);
boxBlurH(array_a->green, array_b->green, w, h, horizontal_radius_value);
boxBlurH(array_a->blue, array_b->blue, w, h, horizontal_radius_value);
boxBlurH(array_a->alpha, array_b->alpha, w, h, horizontal_radius_value);
}

// Swap input and output arrays
channels *temp = array_a;
array_a = array_b;
array_b = temp;
boxBlurH(frame_image->bits(), frame_image_2->bits(), w, h, horizontal_radius_value);

// Swap output image back to input
frame_image.swap(frame_image_2);
}

// VERTICAL BLUR (if any)
if (vertical_radius_value > 0.0) {
// Apply vertical blur to target RGBA channels
#pragma omp parallel
{
boxBlurT(array_a->red, array_b->red, w, h, vertical_radius_value);
boxBlurT(array_a->green, array_b->green, w, h, vertical_radius_value);
boxBlurT(array_a->blue, array_b->blue, w, h, vertical_radius_value);
boxBlurT(array_a->alpha, array_b->alpha, w, h, vertical_radius_value);
}
boxBlurT(frame_image->bits(), frame_image_2->bits(), w, h, vertical_radius_value);

// Swap input and output arrays
channels *temp = array_a;
array_a = array_b;
array_b = temp;
// Swap output image back to input
frame_image.swap(frame_image_2);
}
}

// Copy RGBA channels back to original image
#pragma omp parallel for
for (int pixel = 0; pixel < w * h; ++pixel)
{
// Combine channels
pixels[pixel * 4] = array_b->red[pixel];
pixels[pixel * 4 + 1] = array_b->green[pixel];
pixels[pixel * 4 + 2] = array_b->blue[pixel];
pixels[pixel * 4 + 3] = array_b->alpha[pixel];
}

// Delete channel arrays
delete[] arrays_in.red;
delete[] arrays_in.green;
delete[] arrays_in.blue;
delete[] arrays_in.alpha;

delete[] arrays_out.red;
delete[] arrays_out.green;
delete[] arrays_out.blue;
delete[] arrays_out.alpha;

// return the modified frame
return frame;
}

// Credit: http://blog.ivank.net/fastest-gaussian-blur.html (MIT License)
// Modified to process all four channels in a pixel array
void Blur::boxBlurH(unsigned char *scl, unsigned char *tcl, int w, int h, int r) {
float iarr = 1.0 / (r + r + 1);
for (int i = 0; i < h; i++) {
int ti = i * w, li = ti, ri = ti + r;
int fv = scl[ti], lv = scl[ti + w - 1], val = (r + 1) * fv;
for (int j = 0; j < r; j++) val += scl[ti + j];
for (int j = 0; j <= r; j++) {
val += scl[ri++] - fv;
tcl[ti++] = round(val * iarr);
}
for (int j = r + 1; j < w - r; j++) {
val += scl[ri++] - scl[li++];
tcl[ti++] = round(val * iarr);
}
for (int j = w - r; j < w; j++) {
val += lv - scl[li++];
tcl[ti++] = round(val * iarr);

#pragma omp parallel for shared (scl, tcl)
for (int i = 0; i < h; ++i) {
for (int ch = 0; ch < 4; ++ch) {
int ti = i * w, li = ti, ri = ti + r;
int fv = scl[ti * 4 + ch], lv = scl[(ti + w - 1) * 4 + ch], val = (r + 1) * fv;
for (int j = 0; j < r; ++j) {
val += scl[(ti + j) * 4 + ch];
}
for (int j = 0; j <= r; ++j) {
val += scl[ri++ * 4 + ch] - fv;
tcl[ti++ * 4 + ch] = round(val * iarr);
}
for (int j = r + 1; j < w - r; ++j) {
val += scl[ri++ * 4 + ch] - scl[li++ * 4 + ch];
tcl[ti++ * 4 + ch] = round(val * iarr);
}
for (int j = w - r; j < w; ++j) {
val += lv - scl[li++ * 4 + ch];
tcl[ti++ * 4 + ch] = round(val * iarr);
}
}
}
}

void Blur::boxBlurT(unsigned char *scl, unsigned char *tcl, int w, int h, int r) {
float iarr = 1.0 / (r + r + 1);

#pragma omp parallel for shared (scl, tcl)
for (int i = 0; i < w; i++) {
int ti = i, li = ti, ri = ti + r * w;
int fv = scl[ti], lv = scl[ti + w * (h - 1)], val = (r + 1) * fv;
for (int j = 0; j < r; j++) val += scl[ti + j * w];
for (int j = 0; j <= r; j++) {
val += scl[ri] - fv;
tcl[ti] = round(val * iarr);
ri += w;
ti += w;
}
for (int j = r + 1; j < h - r; j++) {
val += scl[ri] - scl[li];
tcl[ti] = round(val * iarr);
li += w;
ri += w;
ti += w;
}
for (int j = h - r; j < h; j++) {
val += lv - scl[li];
tcl[ti] = round(val * iarr);
li += w;
ti += w;
for (int ch = 0; ch < 4; ++ch) {
int ti = i, li = ti, ri = ti + r * w;
int fv = scl[ti * 4 + ch], lv = scl[(ti + w * (h - 1)) * 4 + ch], val = (r + 1) * fv;
for (int j = 0; j < r; j++) val += scl[(ti + j * w) * 4 + ch];
for (int j = 0; j <= r; j++) {
val += scl[ri * 4 + ch] - fv;
tcl[ti * 4 + ch] = round(val * iarr);
ri += w;
ti += w;
}
for (int j = r + 1; j < h - r; j++) {
val += scl[ri * 4 + ch] - scl[li * 4 + ch];
tcl[ti * 4 + ch] = round(val * iarr);
li += w;
ri += w;
ti += w;
}
for (int j = h - r; j < h; j++) {
val += lv - scl[li * 4 + ch];
tcl[ti * 4 + ch] = round(val * iarr);
li += w;
ti += w;
}
}
}
}
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