Get width and height of scaled down image after imagerotation? - php

Question

A followup to this question:
How to get new width and height after an image has been rotated with imagerotate()?
The answer I got is based on the filenames actual image size, but if I want to start from another width and height.
How would I achieve that? See below code for my attempt...
$ps['product_angle'] = 77; //Could be any angle
$filename = 'test.png' //filename to the original product
list($source_width, $source_height) = getimagesize($filename);
$source_image = imagecreatefromjpeg($filename);
//Example for clarification (this is parameters that is used to save new image)
$ps['product_width'] = 40; //for example $source_width = 200
$ps['product_height'] = 80; //and $source_height = 400
$angle = $ps['product_angle'];
if (intval($angle) <> 0) {
//Actual dimensions of image from filename
$current_source_x = imagesx($source_image);
$current_source_y = imagesy($source_image);
//Get current ratio of "scaled down image"
$ratio_x = $ps['product_width'] / $current_source_x;
$ratio_y = $ps['product_height'] / $current_source_y;
$source_image = imagerotate(
$source_image,
360-$angle,
imageColorAllocateAlpha($source_image, 255, 255, 255, 127)
);
//New dimensions from actual filename
//This would be fine if I just wanted the new width and height
//based on the filenames dimension, but I want new dimensions
//for the "scaled downed version" of the image (40, 80)
$new_image_source_x = imagesx($source_image);
$new_image_source_y = imagesy($source_image);
//I tried this, but obviously I'm doing something totally wrong
$new_width = ($new_image_source_x - $current_source_x) * $ratio_x;
$new_height = ($new_image_source_y - $current_source_y) * $ratio_y;
//Set new width after rotation
$ps['product_width'] = $new_width;
$ps['product_height'] = $new_height;
}
$ps['source_image'] = $source_image;
list($source_width, $source_height) = getimagesize($filename);
$dest_width = (int)$ps['product_width'];
$dest_height = (int)$ps['product_height'];
//Resize source-image to new width and height
//
imagecopyresized($dest_image, $ps['source_image'], 0, 0, 0, 0, $dest_width, $dest_height, $source_width, $source_height);
Probably I'm missing something very essential....
UPDATE
An example of real values...
image current width63.224619257754
image current height80.210337864315
//after calculation
image new width37.583523669887
image newt height21.716336015666
where angle is 41.10419020401479

Answer 1

Looking at my comment
"I've actually came into a solution"
.. It wasn't the day when I used my best english skills...
I guess you know what I meant though and here is how I solved my issue:
In my approach I was trying to calculate the new values based on ratio from the "scaled down image" and then get new width and height based on the difference from the "scaled down image" and "the image after rotated".
Something like this:
Set the relation/ratio between "scaled down image" and original image.
Do the actual image-rotation
Get the difference between original dimensions from the rotated image and multiply that with ratio-factor set before image was rotated.
Get the new width and height based on the rotation angle
This really didn't work correctly (failed at step4). I've been looking around a lot to find answers how to calculate width and height after an image is rotated. But these width and heights didn't return the same dimensions that the GD-functions imagesx() and imagesy() returned after the image was rotated. I've tried out several of calculations using sin() and cos() for retrieving the width and height but still didn't get exact same values as imagesx() and imagesy().
That got me thinking... What if I change my approach to:
Set the relation/ratio between "scaled down image" and original image.
Do the actual image-rotation
Apply the new dimensions based on the ratio multiplied with imagesx() and imagesy() - values return after the rotation
New code:
//Rotate resized image (if it should be)
$angle = $ps['product_angle'];
if (intval($angle) <> 0) {
//Get current dimensions from file
$current_source_x = imagesx($source_image);
$current_source_y = imagesy($source_image);
//Get current ratio of "scaled down image"
$ratio_x = $ps['product_width'] / $current_source_x;
$ratio_y = $ps['product_height'] / $current_source_y;
//Rotate image
$source_image = imagerotate($source_image, 360-$angle, imageColorAllocateAlpha($source_image, 255, 255, 255, 127));
//Now we get a new width from the imagerotate()-function, use those to set new_width from
//ratio/propoprtions is used from origin width and height
$ps['product_width'] = imagesx($source_image) * $ratio_x;
$ps['product_height'] = imagesy($source_image) * $ratio_y;
}
This worked fine - almost... the issue now was that the if the rotated image's new width and/or height got larger then the origin dimensions of the image, then the proportions wouldn't be accurate (and would cut off the imagesometimes (depending the rotation angle)).
The code was modified so heights and widths would be in proportion to the image from the file when creating the resized image.
//Rotate resized image (if it should be)
$angle = $ps['product_angle'];
if (intval($angle) <> 0) {
//Get current dimensions from file
$current_source_x = imagesx($source_image);
$current_source_y = imagesy($source_image);
//Get current ratio of "scaled down image"
$ratio_x = $ps['product_width'] / $current_source_x;
$ratio_y = $ps['product_height'] / $current_source_y;
//Rotate image
$source_image = imagerotate($source_image, 360-$angle, imageColorAllocateAlpha($source_image, 255, 255, 255, 127));
//Now we get a new width from the imagerotate()-function, use those to set new_width from
//ratio/propoprtions is used from origin width and height
$ps['product_width'] = imagesx($source_image) * $ratio_x;
$ps['product_height'] = imagesy($source_image) * $ratio_y;
//Set these so we can modifiy the width and height given from getimagesize()-function below
$ps['source_width'] = imagesx($source_image) ;
$ps['source_height'] = imagesy($source_image);
}
//If image is rotated, then width and height are adjusted with these values
if (isset($ps['source_width']) && isset($ps['source_height']) ) {
$source_width = $ps['source_width'];
$source_height = $ps['source_height'];
}
//Set position where to place in the image to save
$dest_x = $ps['product_left'];
$dest_y = $ps['product_top'];
$dest_width = (int)$ps['product_width'];
$dest_height = (int)$ps['product_height'];
//Resize source-image to new width and height and then copy from source to destination point
imagecopyresized($dest_image, $ps['source_image'], $dest_x, $dest_y, 0, 0, $dest_width, $dest_height, $source_width, $source_height);
So my final solution would include these steps:
Set the relation/ratio between "scaled down image" and original image.
Do the actual image-rotation
Apply the new dimensions based on the ratio multiplied with imagesx() and imagesy() - values return after the rotation
Set "fake" width and height when image has been rotated, so the resizing would work in proportion to the original image.
I hope this would help anyone who's struggling with the same issue I've struggled with (a few hours to much)!