Trimming An Image Canvas With ImageUtils.cfc ColdFusion Image Component

Posted February 27, 2008 at 9:17 AM by Ben Nadel

Tags: ColdFusion

I'm not gonna bother posting the code here, since it's in the ImageUtils.cfc RIA Forge project, but I created two new methods for trimming a ColdFusion image canvas:

TrimCanvas( Image, BackgroundColor [, Tolerance ] )

This will take a ColdFusion image object and, given the background color, it will reduce the size of the canvas to the smallest possible rectangle without hurting any of the primary image data. You can pass in an optional tolerance value. The tolerance allows some flexibility when it comes to matching the current pixel color to the given background color. The tolerance is the allowable delta in any given color channel (0 to 255).

TrimCanvasSide( Image, Side, BackgroundColor [, Tolerance ] )

This will trim just the given side of the canvas. In reality, TrimCanvas() internally calls this method four times - once per side.

These are SLOW functions. This should not be something that is done on the fly, but rather something that is done to prepare a future-static image. That being said, let's take a look at some sample code:

  • <!--- Create the image utils object. --->
  • <cfset objImageUtils = CreateObject(
  • "component",
  • "imageutilsroot.imageUtils"
  • ).Init()
  • />
  •  
  •  
  • <!--- Create a large, off-white canvas. --->
  • <cfset objImage = ImageNew(
  • "",
  • 300,
  • 300,
  • "argb",
  • "##F5F5F5"
  • ) />
  •  
  • <!--- Set the drawing color. --->
  • <cfset ImageSetDrawingColor(
  • objImage,
  • "##FF9900"
  • ) />
  •  
  • <!--- Draw a circle in the middle of the canvas. --->
  • <cfset ImageDrawOval(
  • objImage,
  • 100,
  • 100,
  • 100,
  • 100,
  • "yes"
  • ) />
  •  
  • <!--- Set up our font properties. --->
  • <cfset objFont = {
  • Size = "20",
  • Font = "Arial Black"
  • } />
  •  
  • <!--- Draw text. --->
  • <cfset ImageDrawText(
  • objImage,
  • "MY FIRST CIRCLE",
  • 45,
  • 250,
  • objFont
  • ) />
  •  
  •  
  • <p>
  • <!--- Write image to browser. --->
  • <cfimage
  • action="writetobrowser"
  • source="#objImage#"
  • />
  • </p>
  •  
  •  
  •  
  •  
  •  
  • <!--- Trim the canvas. --->
  • <cfset objImage = objImageUtils.TrimCanvas(
  • objImage,
  • "##F5F5F5"
  • ) />
  •  
  • <p>
  • <!--- Write image to browser. --->
  • <cfimage
  • action="writetobrowser"
  • source="#objImage#"
  • />
  • </p>

In this demo, we are creating a canvas with a centered circle and some text. Then we are outputting it. Then, we are trimming the canvas and outputting the smaller canvas. Running the above code, we get the following output:


 
 
 

 
Trimming ColdFusion Image Canvas - Before Trimming  
 
 
 

 
 
 

 
Trimming ColdFusion Image Canvas - After Trimming  
 
 
 

As you can see, the excess "background color" was trimmed away from our original image leaving the smallest possible canvas that contained all of the primary image data. Again, this is a very SLOW function. This demo took several seconds to run and the image that we are working on is rather small. This is not something you are going to want to run all the time. Hopefully, I can think of a better, faster way to do this.




Reader Comments

Aug 17, 2009 at 2:38 PM // reply »
46 Comments

I haven't been able to get this method to work. I've posted an issue regarding it in Riaforge.


Post A Comment

Comment Etiquette: Please do not post spam. Please keep the comments on-topic. Please do not post unrelated questions or large chunks of code. And, above all, please be nice to each other - we're trying to have a good conversation here.

Please review the following issues:

Author Name:


Author Email:

Author Website:

Comment:

Supported HTML tags for formatting: <strong>bold</strong>   <em>italic</em>   <code>code</code>







  • Help Wanted - Find Your Next ColdFusion Job
Ben Nadel's Company - Epicenter Consulting Recent Blog Comments
May 21, 2013 at 6:12 PM
Using Plupload For Drag & Drop File Uploads In ColdFusion
Ben, I did not see you after Pete Freitag's Lockdown session at cfObjective but he said that IIS sets file size limits at 30MB by default which just happened to be the threshold for file size when ... read »
May 21, 2013 at 11:51 AM
Ask Ben: Parsing Very Large XML Documents In ColdFusion
Looking at my first ever XML document that I have to parse and put into MS SQL 2000 with CF8. I get it to list the desired Field name, many times over, and have a long list of this field name displa ... read »
May 21, 2013 at 9:25 AM
Turning Off and On Identity Column in SQL Server
you are awesome..i am lucky to get this blog between such a garbage one....Thanks, Prashant ... read »
May 20, 2013 at 4:38 PM
Using A Dynamic Column Name With ValueList() In ColdFusion
@Dana, Your confusion is well founded, since this is a very confusing features. In fact, it ONLY works if you use array notation. Meaning, that this: arrayToList( query[ "columnName" ] ) ... read »
May 20, 2013 at 4:34 PM
Using A Dynamic Column Name With ValueList() In ColdFusion
I was thinking chicken and the egg, I wouldn't have expected it to work in the valuelist going in I guess. Maybe I just need a beer, long day :) ... read »
May 20, 2013 at 4:29 PM
Using A Dynamic Column Name With ValueList() In ColdFusion
@Dana, That's if you're trying to reference a specific row. In this case, we're trying to reference the entire query column as one cohesive value. So, you are correct that if you wanted to output a ... read »
May 20, 2013 at 4:24 PM
Using A Dynamic Column Name With ValueList() In ColdFusion
I thought when you used array notation to reference queries you always had to have the row or it would throw a similar error as well? ... read »
May 20, 2013 at 11:45 AM
Using jQuery's Animate() Step Callback Function To Create Custom Animations
This is really useful. I found out that you don't actually have to use a dummy css property (surprisingly). To animate a property in a linear-gradient for instance I did this this.css('someLinearGra ... read »
InVision App - Prototyping Made Beautiful With Prototyping Tools