/// <summary>
/// Calculates how much of the bottom of bitmap1 is the same as the top of bitmap2.
/// </summary>
public static int CalculateVerticalOverlap(Bitmap bitmap1, Bitmap bitmap2, IColorComparer comparer, int maxDifference)
{
if (bitmap1.Width != bitmap2.Width)
{
return(0);
}
using (var data1 = new LockedBitmapData(bitmap1))
using (var data2 = new LockedBitmapData(bitmap2))
{
// If bitmap2 is shorter than bitmap1, start further down, otherwise start at 0.
int startY = Math.Max(0, bitmap1.Height - bitmap2.Height);
for (int y1 = startY; y1 < bitmap1.Height; y1++)
{
if (CalculateBitmapRectDifference(data1, new Point(0, y1), data2, new Point(0, 0), new Size(bitmap1.Width, bitmap1.Height - y1), comparer, maxDifference) <= maxDifference)
{
return(bitmap1.Height - y1);
}
}
return(0);
}
}
private static bool IsHorizontalLineWithColor(LockedBitmapData data, int y, Color color, IColorComparer comparer)
{
for (int x = 0; x < data.Bitmap.Width; x++)
{
if (!comparer.Compare(data.GetPixel(x, y), color))
{
return(false);
}
}
return(true);
}
/// <summary>
/// Checks whether all pixels within a row of a bitmap are the specified color.
/// </summary>
/// <param name="bitmap">The bitmap to check</param>
/// <param name="y">The row of the bitmap to check</param>
/// <param name="color">The color to check the row against</param>
/// <param name="comparer">The comparer to use to compare the pixels against the specified color</param>
/// <returns>Whether all the pixels within the row are the specified color</returns>
public static bool IsHorizontalLineWithColor(Bitmap bitmap, int y, Color color, IColorComparer comparer)
{
using (var data = new LockedBitmapData(bitmap))
{
return(IsHorizontalLineWithColor(data, y, color, comparer));
}
}
/// <summary>
/// Finds the first row within a bitmap for which all the pixels are the specified color.
/// The search begins at the specified row and contains downwards until a match is found.
/// </summary>
/// <param name="bitmap">The bitmap to check</param>
/// <param name="startY">The first row of the bitmap to check</param>
/// <param name="color">The color to check rows against</param>
/// <param name="comparer">The comparer to use to compare the pixels against the specified color</param>
/// <returns>The Y coordinate of the first row which is the specified color, or null if none were found</returns>
public static int?FindHorizontalLineWithColor(Bitmap bitmap, int startY, Color color, IColorComparer comparer)
{
using (var data = new LockedBitmapData(bitmap))
{
for (int y = startY; y < bitmap.Height; y++)
{
if (IsHorizontalLineWithColor(data, y, color, comparer))
{
return(y);
}
}
}
return(null);
}
private static int CalculateBitmapRectDifference(LockedBitmapData data1, Point offset1, LockedBitmapData data2, Point offset2, Size size, IColorComparer comparer, int?maxDifference = null)
{
int diffs = 0;
for (int y = 0; y < size.Height; y++)
{
for (int x = 0; x < size.Width; x++)
{
var col1 = data1.GetPixel(x + offset1.X, y + offset1.Y);
var col2 = data2.GetPixel(x + offset2.X, y + offset2.Y);
if (!comparer.Compare(col1, col2))
{
diffs++;
if (maxDifference.HasValue && diffs > maxDifference.Value)
{
return(diffs);
}
}
}
}
return(diffs);
}
/// <summary>
/// Calculates the number of pixels that are different between a region of a test bitmap and a reference bitmap.
/// </summary>
/// <param name="bitmap">The test bitmap</param>
/// <param name="offset">The offset from the top left of the test bitmap of the region to be compared
/// against the reference bitmap</param>
/// <param name="refBitmap">The reference bitmap</param>
/// <param name="comparer">The comparer to use to compare pixels of the two bitmaps</param>
/// <param name="maxDifference">The maximum number of different pixels before the comparision will stop early.
/// If null, all pixels will be compared.</param>
/// <returns>The number of different pixels</returns>
public static int CalculateDifference(Bitmap bitmap, Point offset, Bitmap refBitmap, IColorComparer comparer, int?maxDifference = null)
{
if (!IsRectWithinRect(bitmap.Size, offset, refBitmap.Size))
{
return(int.MaxValue);
}
using (var data1 = new LockedBitmapData(bitmap))
using (var data2 = new LockedBitmapData(refBitmap))
{
return(CalculateBitmapRectDifference(data1, offset, data2, new Point(0, 0), refBitmap.Size, comparer, maxDifference));
}
}
