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Ben Nadel at cf.Objective() 2014 (Bloomington, MN) with: Gert Franz
Ben Nadel at cf.Objective() 2014 (Bloomington, MN) with: Gert Franz ( @gert_railo )

Anti-Aliasing Has No Effect On Image Resizing / Scaling In ColdFusion

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There's nothing in the ColdFusion documentation that states that anti-aliasing will have any affect on image resizing or scaling. However, many of the code samples in the documentation turn anti-aliasing "ON" before performing a image resize action. As such, there's a lot of confusion as to whether or not anti-aliasing is doing anything (for resize action). So, I decided to run some quick tests. And, from what I can tell, anti-aliasing has no affect on the speed of resizing or the quality of the generated thumbnail.

To test this, I took a number of images and resized them twice. On the first pass, I resized them without anti-aliasing; on the second pass, I resized then with anti-aliasing enabled:

<cfoutput>

	<!--- Read list of test files to work on. --->
	<cfset imagePaths = directoryList( expandPath( "./images/" ), false, "path" ) />

	<table cellpadding="20" cellspacing="5" border="1">

		<cfloop index="imagePath" array="#imagePaths#">

			<tr>
				<!--- Test without anti-aliasing. --->
				<td align="center">

					<cfset filename = getFileFromPath( imagePath ) />
					<cfset thumbPath = "./thumbs/#filename#" />

					<cfset startedAt = getTickCount() />

					<!--- Scale image WITHOUT anti-aliasing. --->
					<cfset image = imageNew( imagePath ) />
					<cfset imageSetAntialiasing( image, "off" ) />
					<cfset imageScaleToFit( image, 300, "", "highPerformance" ) />

					<cfset endedAt = getTickCount() />

					<cfset imageWrite( image, thumbPath ) />

					<img src="#thumbPath#" /><br />

					#( endedAt - startedAt )# ms
					&mdash;
					#getFileInfo( expandPath( thumbPath ) ).size# Bytes

				</td>

				<!--- Test with anti-aliasing. --->
				<td align="center">

					<cfset filename = getFileFromPath( imagePath ) />
					<cfset thumbPath = "./thumbs-antialiased/#filename#" />

					<cfset startedAt = getTickCount() />

					<!--- Scale image WITH anti-aliasing. --->
					<cfset image = imageNew( imagePath ) />
					<cfset imageSetAntialiasing( image, "on" ) />
					<cfset imageScaleToFit( image, 300, "", "highPerformance" ) />

					<cfset endedAt = getTickCount() />

					<cfset imageWrite( image, thumbPath ) />

					<img src="#thumbPath#" /><br />

					(Anti-Aliasing) #( endedAt - startedAt )# ms
					&mdash;
					#getFileInfo( expandPath( thumbPath ) ).size# Bytes

				</td>
			</tr>

		</cfloop>

	</table>

</cfoutput>

When we run the above code, we get the following page output:

The affect of anti-aliasing on image resizing / scaling in ColdFusion.

As you can see there is no visual difference, meaningful speed difference, or file-size difference between the two thumbnails despite a difference in the anti-aliasing setting.

Of course, I didn't want to rely on my own level of perception; so, I put the two sets of thumbnails in Adobe Fireworks and applied a "difference" to the two layers. The result demonstrated that there was zero difference, at the pixel level, between the two sets of thumbnails.

In my mind, it is now clear - despite some misleading code samples, anti-aliasing has no affect on image resizing in ColdFusion. Of course, anti-aliasing does have an affect on other aspects of image manipulation; but, enabling will not provide any benefit in terms of image resizing.

Want to use code from this post? Check out the license.

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Ben Nadel