C ++指针错误（访问冲突）

Question

I am new to C++ and think I am probably doing something I shouldn't be with pointers. I've checked tons of resources, but just can't find the problem. After debugging for a while it looks like this is the problem code.

writeHeader(outFile, width, height); 
for (int row=0; row < width+1; row++){ // row == 0 is the bottom row
    for (int col=0; col < height+1; col++){ // col == 0 is the leftmost column
    Color c =  getPixel(row, col);
    outFile.write((char*)c.blue, 1);
    outFile.write((char*)c.green, 1);
    outFile.write((char*)c.red, 1);
    }
}

can anyone see what is wrong?

The getPixel method looks like this.

Color BMPCanvas::getPixel(int x, int y){
if (x<=width && y<=height){
        return image[y*width + x];
    }
    return Color(0,0,0);
}

EDIT: I changed the above code to:

    for (int row=0; row < width; row++){ // row == 0 is the bottom row
        for (int col=0; col < height; col++){ // col == 0 is the leftmost column
        Color c =  getPixel(row, col);
        unsigned char green = c.green, blue = c.blue, red = c.red;
        outFile.write((char*)&blue, 1);
        outFile.write((char*)&green, 1);
        outFile.write((char*)&red, 1);
        }
    }

which I believe fixed one of the problems, but I am still getting a memory error. Green blue and red refer to numbers referring to their color value such as (255,255,255).

I truly appreciate the help.

Answer 1

My best guess would be you have an "off by one" error. C++ arrays are zero based and so when you have an array with 10 slots you iterate from 0 to 9, not 0 to 10.

Try changing getPixel to this:

Color BMPCanvas::getPixel(int x, int y){
if (x<width && y<height){
        return image[y*width + x];
    }
    return Color(0,0,0);
}

And your other loop to this:

for (int row=0; row < width; row++){ // row == 0 is the bottom row
    for (int col=0; col < height; col++){ // col == 0 is the leftmost column