Ios – UIImageView keep aspect ratio, but fit to width

aspect-ratioiosswiftuiimageuiimageview

I have a UIImageView with a fixed width and height. I don't want to change the frame of the UIImageView. I want to have it hold an image where I keep the aspect ratio and I fit the width and let the image be either too tall, or too short for the UIImageView's frame. Like this:

The red is the UIImageView's frame. The gray is the actual image as it's displayed.

Best Answer

I think the best way to do it is to play with the mode of your imageView (Aspect Fill, Aspect Width, etc) and this is based on the ratio between the width and height of the image

if image.width > image.height {
    imageView.contentMode = UIViewContentModeScaleAspectFit
    //since the width > height we may fit it and we'll have bands on top/bottom
} else {
  imageView.contentMode = UIViewContentModeScaleAspectFill
  //width < height we fill it until width is taken up and clipped on top/bottom
}

UIViewContentModeScaleAspectFit

Scales the content to fit the size of the view by maintaining the aspect ratio. Any remaining area of the view’s bounds is transparent.

UIViewContentModeScaleAspectFill

Scales the content to fill the size of the view. Some portion of the content may be clipped to fill the view’s bounds.

I haven't tested it but off the top of my head this seems right

Related Solutions

Html – Maintain the aspect ratio of a div with CSS

Just create a wrapper <div> with a percentage value for padding-bottom, like this:

.demoWrapper {
  padding: 10px;
  background: white;
  box-sizing: border-box;
  resize: horizontal;
  border: 1px dashed;
  overflow: auto;
  max-width: 100%;
  height: calc(100vh - 16px);
}

div {
  width: 100%;
  padding-bottom: 75%;
  background: gold; /** <-- For the demo **/
}

<div class="demoWrapper">
  <div></div>
</div>

It will result in a <div> with height equal to 75% of the width of its container (a 4:3 aspect ratio).

This relies on the fact that for padding :

The percentage is calculated with respect to the width of the generated box's containing block [...] (source: w3.org, emphasis mine)

Padding-bottom values for other aspect ratios and 100% width :

aspect ratio  | padding-bottom value
--------------|----------------------
    16:9      |       56.25%
    4:3       |       75%
    3:2       |       66.66%
    8:5       |       62.5%

Placing content in the div :

In order to keep the aspect ratio of the div and prevent its content from stretching it, you need to add an absolutely positioned child and stretch it to the edges of the wrapper with:

div.stretchy-wrapper {
  position: relative;
}

div.stretchy-wrapper > div {
  position: absolute;
  top: 0; bottom: 0; left: 0; right: 0;
}

Here's a demo and another more in depth demo

Ios – Resize UIImage by keeping Aspect ratio and width

The method of Srikar works very well, if you know both height and width of your new Size. If you for example know only the width you want to scale to and don't care about the height you first have to calculate the scale factor of the height.

+(UIImage*)imageWithImage: (UIImage*) sourceImage scaledToWidth: (float) i_width
{
    float oldWidth = sourceImage.size.width;
    float scaleFactor = i_width / oldWidth;

    float newHeight = sourceImage.size.height * scaleFactor;
    float newWidth = oldWidth * scaleFactor;

    UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight));
    [sourceImage drawInRect:CGRectMake(0, 0, newWidth, newHeight)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newImage;
}

Best Answer

Related Solutions

Html – Maintain the aspect ratio of a div with CSS

Ios – Resize UIImage by keeping Aspect ratio and width

Related Topic