The poster is showing a dimension constrained by height in most cases he posted >>> (256x256, 1024x768, 500x400, 205x246, etc.) but fitting a 64px max height pixel dimension, typical of most landscape "photos". So my guess is he wants an image that is always 64 pixels in height. To achieve that, do the following:
<img id="photo1" style="height:64px;width:auto;" src="photo.jpg" height="64" />
This solution guarantees the images are all 64 pixels max in height and allows width to extend or shrink based on each image's aspect ratio. Setting height to 64 in the img height
attribute reserves a space in the browser's Rendertree layout as images download, so the content doesn't shift waiting for images to download. Also, the new HTML5 standard does not always honor width and height attributes. They are dimensional "hints" only, not final dimensions of the image. If in your style sheet you reset or change the image height and width, the actual values in the images attributes get reset to either your CSS value or the images native default dimensions. Setting the CSS height
to "64px" and the width
to "auto" forces width to start with the native image width (not image attribute width) and then calculate a new aspect-ratio using the CSS style for height. That gets you a new width. So the height and width "img" attributes are really not needed here and just force the browser to do extra calculations.