Delphi – Crop scale and center image with delphi

cropdelphiimagescale

Does anyone know a way of cropping, scaling and centering an image (jpg or bitmap) using Delphi?
I have an image with large resolution. I would like to be able to scale it to a lower resolution. The ratio of the target resolution may be different from the original image. I want to keep the original photo aspect ratio, therefore, I don't want to stretch to the new resolution, but crop and center it, to fit best and loose minimal data from the original image. Does anyone know how can it be done using Delphi?

Best Answer

I'm guessing that you want to resize to fill the target image edge to edge, and crop the part that goes out of bounds.

Here's pseudocode. The implementation will differ depending on what you're working with.

// Calculate aspect ratios
sourceAspectRatio := souceImage.Width / sourceImage.Height;
targetAspectRatio := targetImage.Width / targetImage.Height;

if (sourceAspectRatio > targetAspectRatio) then
begin
  // Target image is narrower, so crop left and right
  // Resize source image
  sourceImage.Height := targetImage.Height;
  // Crop source image
  ..
end
else
begin
  // Target image is wider, so crop top and bottom
  // Resize source image
  sourceImage.Width := targetImage.Width;
  // Crop source image
  ..
end;

Related Solutions

Html – How to stretch an image to fill a
while keeping the image’s aspect-ratio

Update 2016:

Modern browser behave much better. All you should need to do is to set the image width to 100% (demo)

.container img {
   width: 100%;
}

Since you don't know the aspect ratio, you'll have to use some scripting. Here is how I would do it with jQuery (demo):

CSS

.container {
    width: 40%;
    height: 40%;
    background: #444;
    margin: 0 auto;
}
.container img.wide {
    max-width: 100%;
    max-height: 100%;
    height: auto;
}
.container img.tall {
    max-height: 100%;
    max-width: 100%;
    width: auto;
}

HTML

<div class="container">
 <img src="http://i48.tinypic.com/wrltuc.jpg" />
</div>
<br />
<br />
<div class="container">
 <img src="http://i47.tinypic.com/i1bek8.jpg" />
</div>

Script

$(window).load(function(){
 $('.container').find('img').each(function(){
  var imgClass = (this.width/this.height > 1) ? 'wide' : 'tall';
  $(this).addClass(imgClass);
 })
})

R – Flash image upload with mandatory crop

I have a bounty running with a very similar question, be sure to take a peek - there isn't anything there yet that does client side resizing, though.

Also, SWFUpload is said to support it in the new Beta, but the feature is very sparsely documented right now. You would probably have to work on it to get it running the way you want.

Best Answer

Related Solutions

Html – How to stretch an image to fill a while keeping the image’s aspect-ratio

R – Flash image upload with mandatory crop

Related Topic

Html – How to stretch an image to fill a
while keeping the image’s aspect-ratio