Skip to content

Commit

Permalink
3x3 convolution addition (#97)
Browse files Browse the repository at this point in the history 
Added a convolution algorithm for a general 3x3 kernel
  • Loading branch information
@pigparty6
pigparty6 authored Apr 3, 2024
1 parent 731a7f4 commit 3881621
Show file tree
Hide file tree
Showing 2 changed files with 183 additions and 0 deletions.
181 changes: 181 additions & 0 deletions sw/airborne/modules/computer_vision/lib/vision/image.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -999,3 +999,184 @@ void image_draw_line_color(struct image_t *img, struct point_t *from, struct poi
}
}
}


/**
* Kernel multiplication for a 3 x 3 kernel.
* Pixels outside the edges are taken to be 0.
* @param[in] source The source values
* @param[in] kernel The kernel values
* @param total The kernel total, set to 1 if the result should not be normalised
* @param setting Variable is used to indicate which pixels the multiplication uses at a specific edges.
* @param YUV A bool that adds an extra pixel offset if the YUV format is used.
*/
uint8_t ker_mul_3x3(uint8_t const *source, int_fast8_t const *kernel, uint8_t total, uint8_t setting, int width, int YUV) {
int value;
int offset = 1 + YUV;

switch (setting) {
default: { // No edge
value = *(source - offset - width) * kernel[0] + *(source - width) * kernel[1] + *(source + offset - width) * kernel[2] +
*(source - offset) * kernel[3] + *source * kernel[4] + *(source + offset) * kernel[5] +
*(source - offset + width) * kernel[6] + *(source + width) * kernel[7] + *(source + offset + width) * kernel[8];
break; }
case 1: { // Upper Edge
value = *(source - offset) * kernel[3] + *source * kernel[4] + *(source + offset) * kernel[5] +
*(source - offset + width) * kernel[6] + *(source + width) * kernel[7] + *(source + offset + width) * kernel[8];
break; }
case 2: { // Lower Edge
value = *(source - offset - width) * kernel[0] + *(source - width) * kernel[1] + *(source + offset - width) * kernel[2] +
*(source - offset) * kernel[3] + *source * kernel[4] + *(source + offset) * kernel[5];
break; }
case 3: { // Left Edge
value = *(source - width) * kernel[1] + *(source + offset - width) * kernel[2] +
*source * kernel[4] + *(source + offset) * kernel[5] +
*(source + width) * kernel[7] + *(source + offset + width) * kernel[8];
break; }
case 4: { // Right Edge
value = *(source - offset - width) * kernel[0] + *(source - width) * kernel[1] +
*(source - offset) * kernel[3] + *source * kernel[4] +
*(source - offset + width) * kernel[6] + *(source + width) * kernel[7];
break; }
case 5: {// Top Left Corner
value = *source * kernel[4] + *(source + offset) * kernel[5] +
*(source + width) * kernel[7] + *(source + offset + width) * kernel[8];
break; }
case 6: {// Top Right Corner
value = *(source - offset) * kernel[3] + *source * kernel[4] +
*(source - offset + width) * kernel[6] + *(source + width) * kernel[7];
break; }
case 7: {// Bottom Left Corner
value = *(source - width) * kernel[1] + *(source + offset - width) * kernel[2] +
*source * kernel[4] + *(source + offset) * kernel[5];
break; }
case 8: {// Bottom Right Corner
value = *(source - offset - width) * kernel[0] + *(source - width) * kernel[1] +
*(source - offset) * kernel[3] + *source * kernel[4];
break; }
}

return (uint8_t) ((int) abs(value) / total);
}

/**
* Image convolution for a 3x3 kernel
* @param[in] input Input image
* @param[in,out] output Output image
* @param[in] kernel The kernel values
*/
void image_convolution_3x3(struct image_t *input, struct image_t *output, int_fast8_t const *kernel, uint8_t kernel_total) {
// Copy buffer pointers
uint8_t *source = input->buf;
uint8_t *dest = output->buf;

// Copy the creation timestamp (stays the same)
output->ts = input->ts;
output->eulers = input->eulers;
output->pprz_ts = input->pprz_ts;

int height = output->h;
int width = output->w;

if (output->type == IMAGE_YUV422) {
// Skip The first U/V value
*dest++ = 127;
source++;

// Top Left Corner
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 5, 2 * width, 1);
source += 2;
*dest++ = 127;

// Upper Edge
for (int x = 1; x < width - 1; x++) {
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 1, 2 * width, 1);
source += 2;
*dest++ = 127;
}

// Top Right Corner
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 6, 2 * width, 1);
source += 2;
*dest++ = 127;

for (int y = 1; y < height - 1; y++) {
// Left Edge
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 3, 2 * width, 1);
source += 2;
*dest++ = 127;

// Middle
for (int x = 1; x < width - 1; x++) {
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 0, 2 * width, 1);
source += 2;
*dest++ = 127;
}

// Right Edge
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 4, 2 * width, 1);
source += 2;
*dest++ = 127;
}

// Bottom Left Corner
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 7, 2 * width, 1);
source += 2;
*dest++ = 127;

// Bottom Edge
for (int x = 1; x < width - 1; x++) {
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 2, 2 * width, 1);
source += 2;
*dest++ = 127;
}

// Bottom Right Corner
*dest = ker_mul_3x3(source, kernel, kernel_total, 8, 2 * width, 1);
} else {
if (output->type == IMAGE_GRAYSCALE) {
// Top Left Corner
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 5, width, 0);
source++;

// Upper Edge
for (int x = 1; x < width - 1; x++) {
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 1, width, 0);
source++;
}

// Top Right Corner
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 6, width, 0);
source++;

for (int y = 1; y < height - 1; y++) {
// Left Edge
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 3, width, 0);
source++;

// Middle
for (int x = 1; x < width - 1; x++) {
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 0, width, 0);
source++;
}

// Right Edge
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 4, width, 0);
source++;
}

// Bottom Left Corner
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 7, width, 0);
source++;

// Bottom Edge
for (int x = 1; x < width - 1; x++) {
*dest++ = ker_mul_3x3(source, kernel, kernel_total, 2, width, 0);
source++;
}

// Bottom Right Corner
*dest = ker_mul_3x3(source, kernel, kernel_total, 8, width, 0);
}
}
}
2 changes: 2 additions & 0 deletions sw/airborne/modules/computer_vision/lib/vision/image.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -126,5 +126,7 @@ void image_draw_line_color(struct image_t *img, struct point_t *from, struct poi
void pyramid_next_level(struct image_t *input, struct image_t *output, uint8_t border_size);
void pyramid_build(struct image_t *input, struct image_t *output_array, uint8_t pyr_level, uint16_t border_size);
void image_gradient_pixel(struct image_t *img, struct point_t *loc, int method, int *dx, int *dy);
uint8_t ker_mul_3x3(uint8_t const *source, int_fast8_t const *kernel, uint8_t total, uint8_t setting, int width, int YUV);
void image_convolution_3x3(struct image_t *input, struct image_t *output, int_fast8_t const *kernel, uint8_t kernel_total);

#endif

0 comments on commit 3881621

Please sign in to comment.