Smartcrop usage in PHP

[jarodium]

Hello

Is it possible for smartcrop achieve the same that jquery focuspoint does?
I would like to pinpoint a reticle in my web interface and extract that particular section in the dimensions I want.

From what I can read in the docs, smartcrop has a few pre-defined constants but I would like to know if it is possible to provide a center point on the image and smartcrop outputs coordinates for me to use in the crop with the dimensions I want. This way, my users can define their point of interest in the image and have a resulting image of Wpx x Hpx centered around that particular point.

Best regards

[jcupitt]

Hi @jarodium,

smartcrop attempts to position the reticule automatically. If you want to set the position yourself, I would thumbnail the whole image, then crop afterwards. So ... set crop to none (the default), then crop the output yourself.

[jarodium]

I see. From the calculations involved with the current code I have borrowed from one of the author's repos, the resulting crop areas sometimes create vips's "extract_area" aka "crop" errors ( because final length sometimes go way beyond image bounds ).
The author also scales before cropping, so it what you have suggested, maybe the solution to make this working.

Thank you once again for your help.

[jarodium]

Hello again

For anyone who is trying to merge Jquery Focus Point coordinates to make a crop here is a rough simple solution:
I will be assuming Y axis setup only, because I start with the image resized to the width I want as per @jcupitt's suggestion.

function coordToOffset(float $coord): float {
    //Takes a Jquery Focus Point coordinate into an offset
    return ($coord + 1) * 0.5;
}

//this assumes the original image was 1420x1920 and we thumbnailed it to 320 width.
$imageWidth = 320;
$imageHeight = 433;

//I want an image with these dimensions
$finalWidth = 320;
$finalHeight = 230;

$focusPointY = -0.28;

$Y = min(1, max(-1, $focusPointY));

//convert $Y coordinate to an offset in % ( this is gives a % from the top. Remove 100- and you will end up with a % from the bottom )
$yPer = 100-intval(round(coordToOffset($Y) * 100));

    //determine where we should we start to crop in Y axis ( X axis is always zero in my use case )
$yPosStart = round(($imageHeight * $yPer) / 100,0);

    //determine where will the crop area will end
$yPosEnd = $yPosStart + $finalHeight;

$yDist = 0;
    
    //if $yPosEnd does exceed the height of the image ( 433 )
    if ($yPosEnd > $imageHeight) {
             //we will check the difference between $yPosEnd and $imageHeight
            $yDist = $yPosEnd - imageHeight;
            
            //with this value in hand we will push $YposStart more to the top
           $yPosStart -= $yDist;
    }

    $vips->crop(0,$yPosStart,$finalWidth,$finalHeight);

This is a rough sketch of the function i am working with.

It does lack some aditional checks to avoid $yPostStart to go out of bounds on the top and it requires previous knowlegde of the end image dimensions. Also, I am always aware of the image sizes since I'm using this in a CMS i am working on, so the designers ( aka master's of the graphicverse xD ) will always be able to provide specific sizes for specific goals, so that is not an issue.

X axis is not accountable for my use case, but one can make the same calculations with safety.
I would like also to add that I have not tested this function against an landscaped image at this time and further improvements will be made as time passes.

Best regards to all