[SOLVED] if($ratio1>$ratio2, how do you know?

[student101]

I hope this is the right section to post this topic /question?

I have an image upload and resize function...

I would like to know the proper ratio information to help resize the image and keep the proportions or aspect ratio.

 

How does this

 work or How should it work? 
[code]$old_x=imagesx($src_img); //width
$old_y=imagesy($src_img); //height
$ratio1=$old_x/$new_h;
$ratio2=$old_y/$new_w;
if($ratio1>$ratio2){
$thumb_w=$new_w;
$thumb_h=$old_y/$ratio1;
}else{
$thumb_h=$new_h;
$thumb_w=$old_x/$ratio2;
}

[Daniel0]

You'll need to know within what size you need to be.

 

$heightMax = 200;
$widthMax = 200;

$width = $widthOrig = imagex($src_img);
$height = $heightOrig = imagey($src_img);

if ($height > $heightMax) {
$width = round(($heightMax / $height) * $width);
$height = $heightMax;
}
if ($width > $widthMax) {
$height = round(($widthMax / $width) * $height);
$width = $widthMax;
}

echo "New size: {$width}x{$height}" . PHP_EOL;
echo "Old size: {$widthOrig}x{$heightOrig}" . PHP_EOL;
echo 'Ratio (before): ' . round($widthOrig/$heightOrig, 3) . PHP_EOL;
echo 'Ratio (after): ' . round($width/$height, 3) . PHP_EOL;

[student101]

Yes I have that in, you also added it in now...

if ($height > $heightMax) { // WHY this
$width = round(($heightMax / $height) * $width); // WHY this 
$height = $heightMax; 
}
if ($width > $widthMax) { // WHY this
$height = round(($widthMax / $width) * $height); // WHY this
$width = $widthMax;
}

[student101]

Daniel0, I hope you understand what I mean...

Why divide or multiply the widths and or heights?

[Daniel0]

Well, if you make e.g. the width 20% smaller then you would need to make the height 20% smaller as well in order to retain the original proportions.

[student101]

Ok, I see what you mean but don't fully understand it as such.

Why not just use;

$width = $width - 20%; 
$height = $height - 20%; 

Why the whole math system?

$height = round(($widthMax / $width) * $height);
$width = $widthMax;

Is there like a hidden manual that only a select few have access to?

[Daniel0]

Because you have to figure out what the growth rate is... I just picked 20% randomly, which would then have a growth rate of 0.8. The $widthMax / $width is that growth rate, and so you multiply it with the $height so the width and height will grow uniformly. Then you do the same again only with width and height switched.

[student101]

Ok cool now it makes more sense,

At least now I can make it do what I need to do.

 

Thank you,

I appreciate the time.

 

Cheers