Windows Ribbon for WinForms, Part 10 – Working With Images

arik — Sat, 24 Oct 2009 04:10:00 GMT

In this post we'll review the ribbon framework images terminology and see how to set images both statically and dynamically in your WinForms application.

More details can be found at Specifying Ribbon Image Resources on MSDN.

Large Images vs. Small Images
Many ribbon controls allow you to specify an image. For example: Button, ComboBox, and Spinner.
Most of these controls have two properties, one for a large image and one for small. The Ribbon framework will choose one of these sizes according to the available screen space and your definitions for group scaling.

Large image is usually of size 32x32 pixels and Small image is usually of size 16x16 pixels.
I say usually, because this can change. The actual image size should be dependent on your chosen resolution and DPI settings. Microsoft recommended sizes for images are as follows:

DPI	Small Image	Large Image
96 dpi	16x16 pixels	32x32 pixels
120 dpi	20x20 pixels	40x40 pixels
144 dpi	24x24 pixels	48x48 pixels
192 dpi	32x32 pixels	64x64 pixels

The images for a ribbon control are exposed via the LargeImage and SmallImage properties.

High Contrast Mode
High Contrast is a windows accessibility feature designed for people who have vision impairment. It can be turned on/off by pressing: Left ALT + Left SHIFT + PRINT SCREEN.

The mode’s main affect is changing the system colors, so that near colors have high contrast.
Now, in order to support high contrast mode in your application, the ribbon framework exposes two extra properties: LargeHighContrastImage and SmallHighContrastImage which allows you to set images specifically for this mode. Here is an example of how an applications usually looks in high contrast mode:

Setting Images Statically
So we’ve mentioned that we have 4 image properties: LargeImage, SmallImage, LargeHighContrastImage and SmallHighContrastImage. And that the size of the images depends on the current system settings.
So we need a way to supply the application different images for these scenarios. Here it is:

<Command Name="cmdCut" Id="1008" LabelTitle="Cut">
   <Command.LargeImages>
     <Image Source="res/CutLargeImage32.bmp" MinDPI="96" />
     <Image Source="res/CutLargeImage40.bmp" MinDPI="120" />
     <Image Source="res/CutLargeImage48.bmp" MinDPI="144" />
     <Image Source="res/CutLargeImage64.bmp" MinDPI="192" />
   </Command.LargeImages>
   <Command.SmallImages>
     <Image Source="res/CutSmallImage16.bmp" MinDPI="96" />
     <Image Source="res/CutSmallImage20.bmp" MinDPI="120" />
     <Image Source="res/CutSmallImage24.bmp" MinDPI="144" />
     <Image Source="res/CutSmallImage32.bmp" MinDPI="192" />
   </Command.SmallImages>
   <Command.LargeHighContrastImages>
     <Image Source="res/CutLargeImage32HC.bmp" MinDPI="96" />
     <Image Source="res/CutLargeImage40HC.bmp" MinDPI="120" />
     <Image Source="res/CutLargeImage48HC.bmp" MinDPI="144" />
     <Image Source="res/CutLargeImage64HC.bmp" MinDPI="192" />
   </Command.LargeHighContrastImages>
   <Command.SmallHighContrastImages>
     <Image Source="res/CutSmallImage16HC.bmp" MinDPI="96" />
     <Image Source="res/CutSmallImage20HC.bmp" MinDPI="120" />
     <Image Source="res/CutSmallImage24HC.bmp" MinDPI="144" />
     <Image Source="res/CutSmallImage32HC.bmp" MinDPI="192" />
   </Command.SmallHighContrastImages>
 </Command>

If you don’t specify all theses images, the ribbon framework will use the available images and resize them according to his needs. Of course, providing the images yourself is the way to get the best results.

Setting Images Dynamically
In this section we’ll see how to dynamically set the images for a button. The end result will look like this:

This time the image doesn’t help, you need to run it yourself to see the code at work.
The “Swap Once” button demonstrates the simplest way to set the LargeImage property programmatically.
The “Swap Image” button demonstrates how to set the image according to the recommended size.

I’ve added a new function to the RibbonLib.Ribbon class, named ConvertToUIImage. Here is how you use it:

void _buttonDropA_OnExecute(PropertyKeyRef key, PropVariantRef currentValue, IUISimplePropertySet commandExecutionProperties)
 {
     // load bitmap from file
     Bitmap bitmap = new System.Drawing.Bitmap(@"..\..\Res\Drop32.bmp");
     bitmap.MakeTransparent();
 
     // set large image property
     _buttonDropA.LargeImage = _ribbon.ConvertToUIImage(bitmap);
 }

If you want to set an image which has the correct size according to the current DPI settings, in order to avoid the ribbon framework from resizing your image, you should check the value of SystemInformation.IconSize.Width.
Large images size should be (SystemInformation.IconSize.Width x SystemInformation.IconSize.Width) and small images size should be (SystemInformation.IconSize.Width/2) x (SystemInformation.IconSize.Width/2).

Here is an example for setting an image according to windows settings:

void _buttonDropB_OnExecute(PropertyKeyRef key, PropVariantRef currentValue, IUISimplePropertySet commandExecutionProperties)
  {
      List<int> supportedImageSizes = new List<int>() { 32, 48, 64 };
 
      Bitmap bitmap;
      StringBuilder bitmapFileName = new StringBuilder();
 
      int selectedImageSize;
      if (supportedImageSizes.Contains(SystemInformation.IconSize.Width))
      { 
          selectedImageSize = SystemInformation.IconSize.Width;
      }
      else
      {
          selectedImageSize = 32;
      }
 
      exitOn = !exitOn;
      string exitStatus = exitOn ? "on" : "off";
 
      bitmapFileName.AppendFormat(@"..\..\Res\Exit{0}{1}.bmp", exitStatus, selectedImageSize);
 
      bitmap = new System.Drawing.Bitmap(bitmapFileName.ToString());
      bitmap.MakeTransparent();
 
      _buttonDropB.LargeImage = _ribbon.ConvertToUIImage(bitmap);
  }

Behind the scenes
What ConvertToUIImage method actually does is creating an instance of a ribbon framework COM object named UIRibbonImageFromBitmapFactory, which implements IUIImageFromBitmap. This interface supplies a function for wrapping a given HBITMAP (handle for bitmap) as an IUIImage interface.
The ribbon image properties work with these instances of IUIImage. Note that the actual creation of UIRibbonImageFromBitmapFactory is done in the RibbonLib.Ribbon InitFramework method.

public IUIImage ConvertToUIImage(Bitmap bitmap)
 {
     if (_imageFromBitmap == null)
     {
         return null;
     }
 
     IUIImage uiImage;
     _imageFromBitmap.CreateImage(bitmap.GetHbitmap(), Ownership.Transfer, out uiImage);
 
     return uiImage;
 }

Bonus
Similar to my implementation of helper classes for Spinner and ComboBox ribbon controls, I’ve added helper classes for Tab, Group and Button controls. These helpers let you change properties of tabs, groups and buttons easily. The button class also exposes an OnExecute event, which facilitate the way you respond to button clicks.

As always, the result of this post is yet another example of using ribbon features in WinForms applications. Find it at Windows Ribbon for WinForms.

That’s it for now,
Arik Poznanski.

Arik Poznanski's Blog : SmallHighContrastImages

Windows Ribbon for WinForms, Part 10 – Working With Images