索贝尔边缘检测，图像卷积

Question

我正在对图像使用 sobel 边缘检测进行作业。我目前正在努力进行梯度操作。编译时收到"二进制运算符'*'的操作数类型错误"错误。我想这可能是因为我将所有像素定义为字母，我不确定下一步应该是什么。任何帮助将不胜感激！提前谢谢你！

public static BufferedImage sobelEdgeDetect(BufferedImage input) {
int img_width = input.getWidth();
int img_height = input.getHeight();
BufferedImage output_img = new BufferedImage(
img_width, img_height, BufferedImage.TYPE_INT_RGB);
for (int x = 0; x < img_width; x++) {
for (int y = 0; y < img_height; y++) {
Color color_at_pos = new Color(input.getRGB(x, y));
int red = color_at_pos.getRed();
int green = color_at_pos.getGreen();
int blue = color_at_pos.getBlue();
int average = (red + green + blue) / 3;
Color A,B,C,D,F,G,H,I;
if(x-1 > 0 && y+1 < img_height){
A = new Color (input.getRGB(x-1,y+1));
} else {
A = Color.BLACK;
}
if(y+1 < img_height){
B = new Color (input.getRGB(x,y+1));
} else {
B = Color.BLACK;
}
if(x+1 < img_width && y+1 < img_height){
C = new Color (input.getRGB(x+1,y+1));
} else {
C = Color.BLACK;
}
if(x-1 > 0){
D = new Color (input.getRGB(x-1,y));
} else {
D = Color.BLACK;
}
if(x+1 < img_width){
F = new Color (input.getRGB(x+1,y));
} else {
F = Color.BLACK;
}
if(x-1 > 0 && y-1 > 0){
G = new Color (input.getRGB(x-1,y-1));
} else {
G = Color.BLACK;
}
if(y-1 > 0){
H = new Color (input.getRGB(x,y-1));
} else {
H = Color.BLACK;
}
if(x+1 > img_width && y-1 > 0){
I = new Color (input.getRGB(x+1,y-1));
} else {
I = Color.BLACK;
}
int gx = (-A + (-2*D) + -G + C + (2*F)+ I);
int gy = (A + (2*B) + C + (-G) + (-2*H) + (-I));
int result = (int)math.sqrt((gx*gx) + (gy*gy));
if (average < 0) {
average = 0;
} else if (average > 255) {
average = 255;
}
Color average_color = new Color(average, average, average);
output_img.setRGB(x, y, average_color.getRGB());
}
} 
return output_img;
}

Answer 1

问题出在颜色的处理中，这里：

int gx = (-A + (-2*D) + -G + C + (2*F)+ I);
int gy = (A + (2*B) + C + (-G) + (-2*H) + (-I));

这是行不通的。

要获得渐变，您必须

• 将每种颜色分开处理
• 以灰度处理图像

我不能告诉你哪一个适合你。

将每种颜色分开处理：

使用此方法，您可以单独处理每种颜色以检测该颜色的边缘

//red:
int redGx = (-A.getRed() + (-2*D.getRed()) + -G.getRed() + C.getRed() + (2*F.getRed())+ I.getRed());
int redGy = ...
//green:
int greenGx = (-A.getGreen()...

手柄为灰色

int redGx = (toGray(A) + (-2*toGray(D)) + -toGray(G) + toGray(C) + (2*toGray(F))+ toGray(I));
int redGy = ...

您必须提供方法toGray/平均颜色

static int toGray(Color col){
return (color.getGreen()+color.getRed()+col.getBlue()) / 3;
}