Compute dimensions (bounding box) of packing algorithm result

Question

I'm using this binary pack code. I'm using its GrowingPacker approach. It works fine, but I have a hard time figuring out the dimensions of the final pack, I mean the bounding box of final result like (xMin, xMax, yMin, yMax). What is the best approach to find it?

Can I use the final values of x, y, w, h for this.root to compute the bounding box?

I'm not sure if it is correct, but currently I'm using a loop like that loop to compute the bounding box of final pack (I'm using C++):

#include <cfloat> // For FLT_MAX

float minX = FLT_MAX;
float minY = FLT_MAX;
float maxW = - FLT_MAX;
float maxH = - FLT_MAX;

for (const Block &block : blocks) {

    if (block.fit) {

        if (block.fit->x < minX)
            minX = block.fit->x;

        if (block.fit->y < minY)
            minY = block.fit->y;

        if (block.fit->w > maxW)
            maxW = block.fit->w;

        if (block.fit->h > maxH)
            maxH = block.fit->h;

    }

}

Answer 1

To calculate the bounding box that encompasses all the bounding boxes in your list of blocks, you need find the minimum and maximum X and Y and then use that to calculate the width and height of the overall bounding box.

Calculating the maximum width and height of the smaller boxes won't work because that will be the size of the widest and highest of the individual smaller boxes, which won't necessarily be the dimensions of the overall bounding box that encompasses all of them.

float minX = FLT_MAX;
float minY = FLT_MAX;
float maxX = - FLT_MAX;
float maxY = - FLT_MAX;

for (const Block &block : blocks) {

    if (block.fit) {

        if (block.fit->x < minX)
            minX = block.fit->x;

        if (block.fit->y < minY)
            minY = block.fit->y;

        if (block.fit->x + block.fit->w > maxX)
            maxX = block.fit->x + block.fit->w;

        if (block.fit->y + block.fit->h > maxY)
            maxY = block.fit->y + block.fit->h;

    }

}

// now that you have the min/max of x and y, calculate overall w and h:
float w = maxX > minX ? maxX - minX : 0.0f;
float h = maxY > minY ? maxY - minY : 0.0f;