本文介绍了一种改进的漫水填充算法，分别通过灰度值和ARGB四个分量进行颜色相似性判断，以实现更精准的图像填充效果。文中详细展示了算法的实现代码，并通过实例验证了算法的有效性。
之前在魔棒工具的文章里写过一个漫水填充算法，实际使用效果并不好。这是因为算法将图片转为灰度再去与种子点的灰度比较。可以想象，这种做法是不合理的（虽然通常都是这么做）。比如两个视觉上相差很明显的颜色，其灰度值很有可能一样或者相差不大（无论你怎么修改RGB三者权重，终归会遇到这种情况）。所以最好是对颜色的ARGB四个分值分开进行比较，如果速度允许，可以计算方差；如果希望速度快一点，就直接计算差值。
1.按灰度检测
/// <summary>
/// 漫水填充 FloodFill()按灰度检测，FloodFill_argb()按四通道分量检测
/// </summary>
/// <param name="src">原图</param>
/// <param name="location">检测点</param>
/// <param name="fillColor">填充颜色</param>
/// <param name="threshould">阈值</param>
/// <returns>填充图，非填充部分为默认值</returns>
unsafe public Bitmap FloodFill(Bitmap src, Point location, Color fillColor, int threshould)
{
try
{
Bitmap srcbmp = src;
Color backColor = srcbmp.GetPixel(location.X, location.Y);
Bitmap dstbmp = new Bitmap(src.Width, src.Height);
int w = srcbmp.Width;
int h = srcbmp.Height;
Stack<Point> fillPoints = new Stack<Point>(w * h);
System.Drawing.Imaging.BitmapData srcbmpData = srcbmp.LockBits(new Rectangle(0, 0, srcbmp.Width, srcbmp.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
System.Drawing.Imaging.BitmapData dstbmpData = dstbmp.LockBits(new Rectangle(0, 0, dstbmp.Width, dstbmp.Height), System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
int stride = srcbmpData.Stride;
byte* srcbuf = (byte*)srcbmpData.Scan0.ToPointer();
byte* dstbuf = (byte*)dstbmpData.Scan0.ToPointer();
int cr = backColor.R, cg = backColor.G, cb = backColor.B, ca = backColor.A;
byte fcr = fillColor.R, fcg = fillColor.G, fcb = fillColor.B;
if (location.X < 0 || location.X >= w || location.Y < 0 || location.Y >= h) return null;
fillPoints.Push(new Point(location.X, location.Y));
int[,] mask = new int[w, h];
while (fillPoints.Count > 0)
{
Point p = fillPoints.Pop();
mask[p.X, p.Y] = 1;
dstbuf[3 * p.X + p.Y * stride] = fcb;
dstbuf[3 * p.X + 1 + p.Y * stride] = fcg;
dstbuf[3 * p.X + 2 + p.Y * stride] = fcr;
if (p.X > 0 && (mask[p.X - 1, p.Y] != 1)
&& Math.Abs(cb - srcbuf[3 * (p.X - 1) + p.Y * stride]) + Math.Abs(cg - srcbuf[3 * (p.X - 1) + 1 + p.Y * stride]) + Math.Abs(cr - srcbuf[3 * (p.X - 1) + 2 + p.Y * stride]) < threshould
)
{
dstbuf[3 * (p.X - 1) + p.Y * stride] = fcb;
dstbuf[3 * (p.X - 1) + 1 + p.Y * stride] = fcg;
dstbuf[3 * (p.X - 1) + 2 + p.Y * stride] = fcr;
fillPoints.Push(new Point(p.X - 1, p.Y));
mask[p.X - 1, p.Y] = 1;
}
if (p.X < w - 1 && (mask[p.X + 1, p.Y] != 1)
&& Math.Abs(cb - srcbuf[3 * (p.X + 1) + p.Y * stride]) + Math.Abs(cg - srcbuf[3 * (p.X + 1) + 1 + p.Y * stride]) + Math.Abs(cr - srcbuf[3 * (p.X + 1) + 2+p.Y * stride]) < threshould
)
{
dstbuf[3 * (p.X + 1) + p.Y * stride] = fcb;
dstbuf[3 * (p.X + 1) + 1 + p.Y * stride] = fcg;
dstbuf[3 * (p.X + 1) + 2 + p.Y * stride] = fcr;
fillPoints.Push(new Point(p.X + 1, p.Y));
mask[p.X + 1, p.Y] = 1;
}
if (p.Y > 0 && (mask[p.X, p.Y - 1] != 1)
&& Math.Abs(cb - srcbuf[3 * p.X + (p.Y - 1) * stride]) + Math.Abs(cg - srcbuf[3 * p.X + 1 + (p.Y - 1) * stride]) + Math.Abs(cr - srcbuf[3 * p.X +2+ (p.Y - 1) * stride]) < threshould
)
{
dstbuf[3 * p.X + (p.Y - 1) * stride] = fcb;
dstbuf[3 * p.X + 1 + (p.Y - 1) * stride] = fcg;
dstbuf[3 * p.X + 2 + (p.Y - 1) * stride] = fcr;
fillPoints.Push(new Point(p.X, p.Y - 1));
mask[p.X, p.Y - 1] = 1;
}
if (p.Y < h - 1 && (mask[p.X, p.Y + 1] != 1)
&& Math.Abs(cb - srcbuf[3 * p.X + (p.Y + 1) * stride]) + Math.Abs(cg - srcbuf[3 * p.X +1+ (p.Y + 1) * stride]) + Math.Abs(cr - srcbuf[3 * p.X +2+ (p.Y + 1) * stride]) < threshould
)
{
dstbuf[3 * p.X + (p.Y + 1) * stride] = fcb;
dstbuf[3 * p.X + 1 + (p.Y + 1) * stride] = fcg;
dstbuf[3 * p.X + 2 + (p.Y + 1) * stride] = fcr;
fillPoints.Push(new Point(p.X, p.Y + 1));
mask[p.X, p.Y + 1] = 1;
}
}
fillPoints.Clear();
srcbmp.UnlockBits(srcbmpData);
dstbmp.UnlockBits(dstbmpData);
return dstbmp;
}
catch (Exception exp)
{
System.Windows.MessageBox.Show(exp.Message);
return null;
}
} public int GetGray(byte r, byte g, byte b)
{
return (int)(r * 77 + g * 151 + b * 28) >> 8;//按权重计算灰度值
}2.按颜色ARGB四分量检测
这里直接计算差值儿没有计算方差，其实效果已经足够。
unsafe public Bitmap FloodFill_argb(Bitmap src, Point location, Color fillColor, int threshould)
{
try
{
Bitmap srcbmp = src;
Color backColor = srcbmp.GetPixel(location.X, location.Y);
Bitmap dstbmp = new Bitmap(src.Width, src.Height);
int w = srcbmp.Width;
int h = srcbmp.Height;
Stack<Point> fillPoints = new Stack<Point>(w * h);
System.Drawing.Imaging.BitmapData bmpData = srcbmp.LockBits(new Rectangle(0, 0, srcbmp.Width, srcbmp.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
System.Drawing.Imaging.BitmapData dstbmpData = dstbmp.LockBits(new Rectangle(0, 0, dstbmp.Width, dstbmp.Height), System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
int stride = bmpData.Stride;
int stridedst = dstbmpData.Stride;
byte* srcbuf = (byte*)bmpData.Scan0.ToPointer();
int* dstbuf = (int*)dstbmpData.Scan0.ToPointer();
int cr = backColor.R, cg = backColor.G, cb = backColor.B, ca = backColor.A;
byte fcr = fillColor.R, fcg = fillColor.G, fcb = fillColor.B;
int fc = fillColor.ToArgb();
if (location.X < 0 || location.X >= w || location.Y < 0 || location.Y >= h) return null;
fillPoints.Push(new Point(location.X, location.Y));
int[,] mask = new int[w, h];
while (fillPoints.Count > 0)
{
Point p = fillPoints.Pop();
mask[p.X, p.Y] = 1;
dstbuf[ p.X + p.Y * w] = fc;
if (p.X > 0 && (mask[p.X - 1, p.Y] != 1)
&& Math.Abs(cb - srcbuf[4 * (p.X - 1) + p.Y * stride]) + Math.Abs(cg - srcbuf[4 * (p.X - 1) + 1 + p.Y * stride]) + Math.Abs(cr - srcbuf[4 * (p.X - 1) + 2 + p.Y * stride]) < threshould
&& Math.Abs(ca - srcbuf[4 * (p.X - 1) +3+ p.Y * stride]) < threshould/2
)
{
dstbuf[ (p.X - 1) + p.Y * w] = fc;
fillPoints.Push(new Point(p.X - 1, p.Y));
mask[p.X - 1, p.Y] = 1;
}
if (p.X < w - 1 && (mask[p.X + 1, p.Y] != 1)
&& Math.Abs(cb - srcbuf[4 * (p.X + 1) + p.Y * stride]) + Math.Abs(cg - srcbuf[4 * (p.X + 1) + 1 + p.Y * stride]) + Math.Abs(cr - srcbuf[4 * (p.X + 1) + 2 + p.Y * stride]) < threshould
&& Math.Abs(ca - srcbuf[4 * (p.X + 1) + 3 + p.Y * stride]) < threshould / 2
)
{
dstbuf[ (p.X + 1) + p.Y * w] = fc;
fillPoints.Push(new Point(p.X + 1, p.Y));
mask[p.X + 1, p.Y] = 1;
}
if (p.Y > 0 && (mask[p.X, p.Y - 1] != 1)
&& Math.Abs(cb - srcbuf[4 * p.X + (p.Y - 1) * stride]) + Math.Abs(cg - srcbuf[4 * p.X + 1 + (p.Y - 1) * stride]) + Math.Abs(cr - srcbuf[4 * p.X + 2 + (p.Y - 1) * stride]) < threshould
&& Math.Abs(ca - srcbuf[4 * p.X +3+ (p.Y - 1) * stride]) < threshould / 2
)
{
dstbuf[ p.X + (p.Y - 1) * w] = fc ;
fillPoints.Push(new Point(p.X, p.Y - 1));
mask[p.X, p.Y - 1] = 1;
}
if (p.Y < h - 1 && (mask[p.X, p.Y + 1] != 1)
&& Math.Abs(cb - srcbuf[4 * p.X + (p.Y + 1) * stride]) + Math.Abs(cg - srcbuf[4 * p.X + 1 + (p.Y + 1) * stride]) + Math.Abs(cr - srcbuf[4 * p.X + 2 + (p.Y + 1) * stride]) < threshould
&& Math.Abs(ca - srcbuf[4 * p.X +3+ (p.Y + 1) * stride]) < threshould /2
)
{
dstbuf[ p.X + (p.Y + 1) *w] = fc;
fillPoints.Push(new Point(p.X, p.Y + 1));
mask[p.X, p.Y + 1] = 1;
}
}
fillPoints.Clear();
srcbmp.UnlockBits(bmpData);
dstbmp.UnlockBits(dstbmpData);
return dstbmp;
}
catch (Exception exp)
{
System.Windows.MessageBox.Show(exp.Message);
return null;
}
}
3.测试
是驴是马，拉出来遛一遛
下图中要处理的图片，向日葵的花心与花瓣，分别为橙色与黄色，灰度值相差很小，右上角有个透明区域，里面有个黑色方框。
使用
调整阈值，为了观察，把透明度也调整一下，点选花瓣
试一下透明区域
结果不错。
扫一扫
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