对于嵌入式设计，我试图在不使用缓冲器的情况下在板上实现sobel的边缘检测。即我正在直接从屏幕上阅读和书写。但是，我可以存储大约一个或两个带宽的数据，以便稍后引用。这是由于董事会提出的限制。但是我遇到了一些问题。无论我是尝试使用sobel还是其他边缘检测算法，我收到的所有信息都是噪音。代码如下，有没有人有任何建议
版本1
void sobelEdgeDetection2() {
int GX[3][3];
int GY[3][3];
int sumX[3];
int sumY[3];
int SUM[3];
int piX = 0;
int piY = 0;
//uint8_t R, G, B = 0;
int I, J = 0;
//UnpackedColour pixVal;
uint16_t *buffer;
// allocate space for even scan lines and odd scan lines
buffer = new uint16_t[_gl->getWidth()];
//buffer for previous line
uint16_t *bufT;
// allocate space for even scan lines and odd scan lines
bufT = new uint16_t[_gl->getWidth()];
// Masks //////////////////////////////////////
//X//
GX[0][0] = -1;
GX[0][1] = 0;
GX[0][2] = 1;
GX[1][0] = -2;
GX[1][1] = 0;
GX[1][2] = 2;
GX[2][0] = -1;
GX[2][1] = 0;
GX[2][2] = 1;
//Y//
GY[0][0] = 1;
GY[0][1] = 2;
GY[0][2] = 1;
GY[1][0] = 0;
GY[1][1] = 0;
GY[1][2] = 0;
GY[2][0] = -1;
GY[2][1] = -2;
GY[2][2] = -1;
for (int Y = 0; Y < _gl->getHeight(); Y++) {
for (int X = 0; X < _gl->getWidth(); X++) {
sumX[0] = sumX[1] = sumX[2] = 0;
sumY[0] = sumY[1] = sumY[2] = 0;
if (Y == 0 || Y == _gl->getHeight() - 1) {
SUM[0] = SUM[1] = SUM[2] = 0;
} else if (X == 0 || X == _gl->getWidth() - 1) {
SUM[0] = SUM[1] = SUM[2] = 0;
} else {
for (I = -1; I <= 1; I++) {
for (J = -1; J <= 1; J++) {
piX = J + X;
piY = I + Y;
pixel16 pix = getPixel(piX, piY);
uint8_t Red = pix.Red;
uint8_t Green = pix.Green;
uint8_t Blue = pix.Blue;
sumX[0] += (Red) * GX[J + 1][I + 1];
sumX[1] += (Green) * GX[J + 1][I + 1];
sumX[2] += (Blue) * GX[J + 1][I + 1];
sumY[0] += (Red) * GY[J + 1][I + 1];
sumY[1] += (Green) * GY[J + 1][I + 1];
sumY[2] += (Blue) * GY[J + 1][I + 1];
}
}
SUM[0] = abs(sumX[0]) + abs(sumY[0]);
SUM[1] = abs(sumX[1]) + abs(sumY[1]);
SUM[2] = abs(sumX[2]) + abs(sumY[2]);
}
if (SUM[0] > 255)
SUM[0] = 255;
if (SUM[0] < 0)
SUM[0] = 0;
if (SUM[1] > 255)
SUM[1] = 255;
if (SUM[1] < 0)
SUM[1] = 0;
if (SUM[2] > 255)
SUM[2] = 255;
if (SUM[2] < 0)
SUM[2] = 0;
int newPixel[3];
newPixel[0] = (255 - ((unsigned char) (SUM[0])));
newPixel[1] = (255 - ((unsigned char) (SUM[1])));
newPixel[2] = (255 - ((unsigned char) (SUM[2])));
pixel16 pix(newPixel[0], newPixel[1], newPixel[2]);
buffer[X] = packColour(pix).packed565;
}
//Need to move cursor back
// draw it
this->paintRow(Point(0, Y), buffer, _gl->getWidth());
}
delete[] buffer;
}
版本2
/**
* https://www.cl.cam.ac.uk/projects/raspberrypi/tutorials/image-processing/edge_detection.html
* 1 Iterate over every pixel in the image
* 2 Apply the x gradient kernel
* 3 Apply the y gradient kernel
* 4 Find the length of the gradient using pythagoras' theorem
* 5 Normalise the gradient length to the range 0-255
* 6 Set the pixels to the new values
*/
void sobelEdgeDetection4() {
UnpackedColour colour;
for (int x = 1; x < _gl->getWidth() - 1; x++) {
for (int y = 1; y < _gl->getHeight() - 1; y++) {
// initialise Gx and Gy to 0
int Gx = 0;
int Gy = 0;
unsigned int intensity = 0;
// Left column
pixel16 pixel = this->getPixel(x - 1, y - 1);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gx += -intensity;
Gy += -intensity;
pixel = this->getPixel(x - 1, y);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gx += -2 * intensity;
pixel = this->getPixel(x - 1, y + 1);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gx += -intensity;
Gy += +intensity;
// middle column
pixel = this->getPixel(x, y - 1);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gy += -2 * intensity;
pixel = this->getPixel(x, y + 1);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gy += +2 * intensity;
// right column
pixel = this->getPixel(x + 1, y - 1);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gx += +intensity;
Gy += -intensity;
pixel = this->getPixel(x + 1, y);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gx += +2 * intensity;
pixel = this->getPixel(x + 1, y + 1);
intensity = pixel.Red + pixel.Green + pixel.Blue;
Gx += +intensity;
Gy += +intensity;
// calculate the gradient length
unsigned int length = (unsigned int) sqrt(
(float) (Gx * Gx) + (float) (Gy * Gy));
// normalise the length to 0 to 255
length = length / 17;
// draw the pixel on the edge image
pixel16 pixel2(length,length,length);
this->setPixel(x, y, pixel2);
}
}
}
第3版
// sobel map for the x axis
const double _SOBEL_Gx[3][3] = { { -1.0, +0.0, +1.0 }, { -2.0, +0.0, +2.0 },
{ -1.0, +0.0, +1.0 } };
// sobel map for the y axis
const double _SOBEL_Gy[3][3] = { { +1.0, +2.0, +1.0 }, { +0.0, +0.0, +0.0 },
{ -1.0, -2.0, -1.0 } };
double get_sobel_gradient(int width, int height, int x, int y) {
double sobel_gradient_x = 0, sobel_gradient_y = 0;
int mx = 0, my = 0, sx = 0, sy = 0;
for (mx = x; mx < x + 3; mx++) {
sy = 0;
for (my = y; my < y + 3; my++) {
if (mx < width && my < height) {
//int r, g, b, idx;
int idx = (mx + width * my) * 3;
pixel16 pixVal = this->getPixel(idx);
//r = pixVal.Red;
//g = pixVal.Green;
//b = pixVal.Blue;
UnpackedColour col = this->packColour(pixVal);
sobel_gradient_x += col.packed565 * _SOBEL_Gx[sx][sy];
sobel_gradient_y += col.packed565 * _SOBEL_Gy[sx][sy];
}
sy++;
}
sx++;
}
return abs(sobel_gradient_x) + abs(sobel_gradient_y);
}
void sobelEdgeDetection3() {
double threshold = 50000.0;
UnpackedColour colour;
for (int y = 0; y < _gl->getHeight(); y++) {
for (int x = 0; x < _gl->getWidth(); x++) {
if (get_sobel_gradient(_gl->getWidth(), _gl->getHeight(), x, y)
>= threshold) {
colour.packed565 = 0x0000; //set white
} else {
colour.packed565 = 0xFFFF; //set black
}
this->setPixel(x, y, colour);
}
}
}
答案 0 :(得分：2)
对于版本1，在分配2个缓冲区（仅使用buffer和bufT）后，创建2个指针以指向当前行和上一行，如下所示：
uint16_t *currentRow = buffer;
uint16_t *prevRow = bufT;
在行循环内，写入currentRow而不是buffer：
pixel16 pix(newPixel[0], newPixel[1], newPixel[2]);
currentRow[X] = packColour(pix).packed565;
因为Sobel过滤器从上一行读取，所以在完成计算后面行的过滤值之前，您不能覆盖一行。因此，在循环结束时，您当前正在调用paintRow()，绘制前一行（如果存在），然后交换缓冲区以使当前成为前一行，而前一行成为新的当前行（在下一次循环中被覆盖）。在最后一行也绘制了当前行，因为否则它将不会是因为外部循环即将终止。
if(Y > 0) // draw the previous row if this is not the first row:
this->paintRow(Point(0, Y-1), prevRow, _gl->getWidth());
if(Y == _gl->getHeight()-1) // draw the current row if it is the last:
this->paintRow(Point(0, Y), currentRow, _gl->getWidth());
// swap row pointers:
uint16_t *temp = prevRow;
prevRow = currentRow;
currentRow = temp;
同样的策略应该适用于其他版本。