jcrop demo no longer works after resizing main image (Updated with Picture)

Question

i am trying to replicate this jcrop demo. Everything works fine except, my original pictures are very large so, as per the manual, i am resizing them on my page like this:

 jQuery('#cropbox').Jcrop({
            onChange: showPreview,
            onSelect: showPreview,
            bgColor: 'white',
            aspectRatio: 1,
            boxWidth: 300,
            boxHeight: 500
        });

the issue is now the second preview window ( id="preview" ) no longer shows what is in the cropped section on the cropbox. Here is an example:

clearly, the preview window doesn't match the area that i am cropping in the first picture.

any idea how to get the preview image to show correctly when you are resizing the main image upfront ??

Answer 1

try this JSFiddle

html:

<img id="cropbox" src="http://homepage.mac.com/davydewit/popacademie/rw_common/themes/blendit/images/header/image1.jpg" />

<br />

<br />
<div id="previewcrop">
<img id="preview" src="http://homepage.mac.com/davydewit/popacademie/rw_common/themes/blendit/images/header/image1.jpg" />
</div>

css:

#previewcrop{
    width: 100px;
    height: 100px;
    overflow: hidden;
    margin-left: 5px;
}

js:

var imgwidth = 849; // width of the image
var imgheight = 423; // height of the image

jQuery('#cropbox').Jcrop({
            onChange: showPreview,
            onSelect: showPreview,
            bgColor: 'white',
            aspectRatio: 1,
            boxWidth: imgwidth/3,
            boxHeight: imgheight/3
        });

function showPreview(coords)
{
    var rx = 100 / coords.w;
    var ry = 100 / coords.h;

    $('#preview').css({
        width: Math.round(rx * imgwidth) + 'px',
        height: Math.round(ry * imgheight) + 'px',
        marginLeft: '-' + Math.round(rx * coords.x) + 'px',
        marginTop: '-' + Math.round(ry * coords.y) + 'px'
    });
};

Answer 2

function showPreview(coords)
{
    if (parseInt(coords.w) > 0)
    {
        var rx = 100 / coords.w;
        var ry = 100 / coords.h;

        jQuery('#preview').css({
            width: Math.round(rx * 800) + 'px',
            height: Math.round(ry * 600) + 'px',
            marginLeft: '-' + Math.round(rx * coords.x) + 'px',
            marginTop: '-' + Math.round(ry * coords.y) + 'px'
        });
    }
}

For (rx * 800), 800 should be the width of your real image. For (ry * 600), 600 should be the width of your real image. I have tested this against an 800x600 image and it works (using Tutorial3.html and modifying it). Also, don't use the width and height of the scaled image, it won't work.