how do Sprite make trim programmatically in cocos2dx? - cocos2d-x

Question

The image can be with transparent pixels.
How do I get the minimum size of a rectangle that fits this image without transparent pixels?
I want to get something like this:
cocos2d::Rect getBoundingBoxTrim(cocos2d::Sprite* sprite);
Perhaps you will not give me an answer, but at least some tips. I will be very grateful to you.

Answer 1

This is just a basic example. You will have to customize it.
Image* img = new Image();
img->initWithImageFile("my file.png");
Then you iterate over each pixel in the image and determine which pixels at the boundary of the image are opaque, and use that to compute a rectangle.
int leftMost;
int rightMost;
int upperMost;
int lowerMost;
unsigned char *data = new unsigned char[img->getDataLen()*x];
data = img->getData();
for(int i=0;i<img->getWidth();i++)
{
for(int j=0;j<img->getHeight();j++)
{
unsigned char *pixel = data + (i + j * img->getWidth()) * x;
// You can see/change pixels' RGBA value(0-255) here !
// unsigned char r = *pixel;
// unsigned char g = *(pixel + 1);
// unsigned char b = *(pixel + 2) ;
unsigned char a = *(pixel + 3);
if (a>0){
// this pixel is opaque. You can use a different threshold for transparency besides 0, depending on how transparent you won't to consider as "transparent".
//Complete yourself:
if(i<leftMost){
leftMost = i;
}
if(i> rightMost){
rightMost = i;
}
if(j> upperMost){
upperMost = j;
}
if(j< lowerMost){
lowerMost = j;
}
}
}
}
In the "Complete yourself" section, you just keep track of the boundary of where the first / last opaque pixel is.
You need four variables, one for each side.
At the end of the loop, you simply create a rectangle using the four points as sides of the rectangle!
If this solves your problem, mark it as correct.