Distance calculation sometimes results in poor quality image

[kiddailey]

Use case

Display an icon at 64x64, using the best possible quality from the icons available, and always display an icon if any are available.

For example, let us say that I specify the following:

• Min Size: 16
• Max Size: 200
• Perfect Size: 64

And let's also say that a site provides the following icon types:

• 16x16 favicon
• 120x120 apple-touch-icon

For the request with my above min/max/perfect parameter, FaviconFetcher will return the 16x16 image due to the distance calculation:

Queue

Size	Distance
16x16	-67.88
120x120	-79.20

However, in this sample use-case, scaling the 16x16 up to 64x64 would look terrible, especially when a much better result would come from scaling down the 120x120.

Feature Request

• Provide a way to specify that FaviconFetcher should return the closest larger icon (vs just the closest), OR
• Provide a way to specify that FaviconFetcher should select the closest larger icon, scale it down to PerfectSize, and return that result

Alternatives

• Consumer could specify a larger MinSize

  • Pro: No code change
  • Con: If no sizes larger than MinSize are available, no icon is returned even if smaller ones exist

• Consumer could ask for a large Max/PerfectSize and perform a scale down on the fetch result separately

  • Pro: No code change
  • Pro: Gives consumer some control over size/quality
  • Con: Won't work in all cases depending on distance calculation, must ask for very large perfect size
  • Con: Allocates more resources to perform scale
  • Con: "PerfectSize" doesn't mean perfect size anymore

• Consumer could ask for a large Max/PerfectSize and embed result directly

  • Pro: No code change
  • Pro: Gives consumer some control over size/quality
  • Con: Won't work in all cases depending on distance calculation, must ask for very large perfect size
  • Con: Uses more resources to display larger-than-necessary image
  • Con: "PerfectSize" doesn't mean perfect size anymore

Thoughts?

[kiddailey]

As a workaround for this, I've implemented a change to the IconImage.Save() method with PR #24 that can take an additional "size" parameter. In this way, the caller can scale the image proportionally when saving.

It's not perfect as the Fetcher will still be storing a collection of potentially large images in memory, but feels like a good compromise for the time being.

Edit: I moved the code for this into the SVG support branch and pull request as I needed it there anyway and closed the original PR. Keeping this open for discussion on the original idea.

Also SkiaSharp's Resize method isn't the best :/