checking uploaded image resolution and details at client side - apache-flex

Question

In flex, what we do, we normally upload the image from flex end and upload it to the server,
i want to know, can we do some details checking, like i want to find out the image resolution(on the client side) before it is uploaded to the server,
There are going to be two profits, first the client doesn't need to wait for long to image get uploaded, and in case if finding the image resolution is on the server end, so it willtake time, even the image to be uploaded is not of expected resolution
second, the user interaction & interface with the flex application will be improved,
so, please give some idea to to this sort of checking from the flex end

Answer 1

If you mean the width/height measuring of a bitmap loaded into your flex app,
width/height is stored in BitmapData structure
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/display/BitmapData.html
For Image flex control it can be accessed with the construction:
// image_control is an instance of mx.controls.Image
var width:Number = 0;
var height:Number = 0;
if (image_control.content is Bitmap)
{
height= (image_control.content as Bitmap).bitmapData.width;
height= (image_control.content as Bitmap).bitmapData.height;
}

Answer 2

I suppose you're speaking of desktop app. Otherwise you woun't be able to touch any local file (you can only init it's uppload to server).
To work with jpg and png you can use com.adobe.images packages of as3corelib. Trere's able to get height/width or resolution of an image.
Although I belive it's better to perform manipulations with images on server-side

Answer 3

For flex, you can use the FileReference.browse function to load file from hard disk. If you want to check the width and height of the image, you can refer to Dmitry Sapelnikov's answer. If you want to check the total bytes of the image, you can try:
var bitmapByteSize:int = bitmap.bitmapData.getPixels(bitmap.bitmapData.rect).length;
Only checking the resolution of the image may not enough. If you need to modify the image, you may take a look on the following:
http://marstonstudio.com/2007/10/19/how-to-take-a-snapshot-of-a-flash-movie-and-automatically-upload-the-jpg-to-a-server-in-three-easy-steps/
It may give you some hints.

Answer 4

Is your Flex app a desktop app? If so you could load the file from the user's hard drive first, such as: http://mariusht.com/blog/2009/04/01/loading-local-images-directly-into-flash-player-10/
And then get the width and height (and probably a way to get the size) before sending it to a server.
BTW, the resolution of any image to be displayed on the web is always 72 DPI. You can't change the resolution of a jpeg or png for example, but you could print them at different resolutions. I think you are actually looking for the dimensions (width / height).