Robert Morrison
9a1838becc
That one evil commit that means you've actually started development like a real developer. But before that you just wrote things
117 lines
3.3 KiB
C#
117 lines
3.3 KiB
C#
using Serilog;
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using SkiaSharp;
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/// <summary>
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/// Helper class to get data from image files
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/// </summary>
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public class ImageProcessing
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{
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/// <summary> Memoization dictionary for the GCD function </summary>
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private static Dictionary<(int, int), int> _gcdMemo = new();
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/// <summary>
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/// Uses the recursive euclidean method to calcuate the GCD of two integers
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/// </summary>
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/// <param name="a">the first integer</param>
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/// <param name="b">the second integer</param>
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/// <exception cref="ArgumentOutOfRangeException">
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/// Thrown when either of the inputs is negative
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/// </exception>
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/// <returns>
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/// The GCD of the inputs
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///</returns>
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private int GCD(int a, int b)
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{
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Log.Debug("calculating GCD for a:{a} b:{b}", a, b);
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if (a < 0)
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{
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throw new ArgumentOutOfRangeException("a", "This function can only accept positive integers");
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}
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if (b < 0)
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{
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throw new ArgumentOutOfRangeException("b", "This function can only accept positive integers");
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}
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/* We can only run this calculation when a is larger than b */
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if (a < b)
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{
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return GCD(b, a);
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}
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/* Check if we have already calculated these inputs */
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if (_gcdMemo.TryGetValue((a, b), out int gcd))
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{
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Log.Debug("Memo hit, returning {gcd}", gcd);
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return gcd;
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}
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/* Otherwise we calculate the GCD and return it */
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/* Note that the recursive nature of this function means we may hit a match more often */
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Log.Debug("No memo hit, running calculation");
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gcd = b == 0 ? a : GCD(b, a % b);
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_gcdMemo.Add((a, b), gcd);
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return gcd;
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}
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/// <summary>
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/// Where possible calculate the aspect ratio of the image at "<paramref name="path"/>
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/// </summary>
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/// <param name="path">
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/// The path to an image file
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/// </param>
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/// <returns>
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/// Either the string representation of the images aspect ratio
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/// or <see langword="null"/>
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/// </returns>
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/// <remarks>
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/// This function may return null if
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/// <list type="bullet">
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/// <item><paramref name="path"/> does not point to an image</item>
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/// <item>The image cannot be handled by SKIA</item>
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/// <item>The image has no size</item>
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/// <item>You don't have permission to read the image</item>
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/// </list>
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/// </remarks>
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public string? GetAspectRatioString(string path)
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{
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/* This function uses some clever abstraction to allow callers to only worry about passing a path */
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return (GetAspectRatioString(LoadImage(path)));
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}
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private SKBitmap? LoadImage(string path)
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{
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try
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{
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using (var stream = File.OpenRead(path))
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{
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var bitmap = SKBitmap.Decode(stream);
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return bitmap;
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}
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}
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catch (Exception e)
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{
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Log.Error(e, "Error decoding image {path}", path);
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return null;
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}
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}
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private string? GetAspectRatioString(SKBitmap? bitmap)
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{
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if (bitmap == null)
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{
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return null;
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}
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int gcd = GCD(bitmap.Width, bitmap.Height);
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int aspectW = bitmap.Width / gcd;
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int aspectH = bitmap.Height / gcd;
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return $"{aspectW}:{aspectH}";
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}
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}
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