Bitmap使用注意事项
报错：对象当前正在其他地方使用System.Drawing.Bitmap如果跨线程使用，或者同时被多方调用，就会报错对象当前正在其他地方使用
解决方案是新开线程就新建一个Bitmap副本，并且保证一个Bitmap对象同时只被一个地方使用
复现这个问题的例子如下：string file="one image path";
System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(file);
Task.Run(() =>
{
try
{
while (true)
{
for (int i = 0; i < bmp.Width; i++)
for (int j = 0; j < bmp.Height; j++)
{
var c1 = bmp.GetPixel(i, j);
}
Thread.Sleep(100);
}
}
catch (Exception ex)
{
}
});
Task.Run(() =>
{
try
{
while (true)
{
for (int i = 0; i < bmp.Width; i++)
for (int j = 0; j < bmp.Height; j++)
{
var c1 = bmp.GetPixel(i, j);
}
Thread.Sleep(100);
}
}
catch (Exception ex)
{
}
});正确的使用方式是：
string file="one image path";
System.Drawing.Bitmap bmp1 = new System.Drawing.Bitmap(file);
Task.Run(() =>
{
try
{
var cpbmp1 = (Bitmap)bmp1.Clone();
while (true)
{
for (int i = 0; i < cpbmp1.Width; i++)
for (int j = 0; j < cpbmp1.Height; j++)
{
var c1 = cpbmp1.GetPixel(i, j);
}
Thread.Sleep(100);
}
}
catch (Exception ex)
{
}
});
Task.Run(() =>
{
try
{
var cpbmp2 = (Bitmap)bmp1.Clone();
while (true)
{
for (int i = 0; i < cpbmp2.Width; i++)
for (int j = 0; j < cpbmp2.Height; j++)
{
var c1 = cpbmp2.GetPixel(i, j);
}
Thread.Sleep(100);
}
}
catch (Exception ex)
{
}
});使用byte[]也会遇到同样的问题
GetPixel效率问题
System.Drawing.Bitmap原生的GetPixel方法效率较低，可以使用C# Bitmap图片GetPixel 和 SetPixel 效率问题中的写法，经过测试，速度大概可以提高7倍。
测试代码如下：
int times = 10;
//no. 2
System.Drawing.Bitmap bmp1 = new System.Drawing.Bitmap(file);
Stopwatch sw = new Stopwatch();
sw.Start();
for (int number = 0; number < times; number++)
for (int i = 0; i < bmp1.Width; i++)
for (int j = 0; j < bmp1.Height; j++)
{
var c1 = bmp1.GetPixel(i, j);
}
sw.Stop();
Console.WriteLine($"{nameof(Bitmap)}:{sw.ElapsedMilliseconds}");
//no. 1
OldLockBitmap oldLockBitmap = new OldLockBitmap(bmp1);
oldLockBitmap.LockBits();
sw.Restart();
for (int number = 0; number < times; number++)
for (int i = 0; i < bmp1.Width; i++)
for (int j = 0; j < bmp1.Height; j++)
{
var c1 = oldLockBitmap.GetPixel(i, j);
}
sw.Stop();
oldLockBitmap.UnlockBits();
Console.WriteLine($"{nameof(OldLockBitmap)}1:{sw.ElapsedMilliseconds}");关于速率问题的讨论：c# faster way of setting pixel colours
https://blog.51cto.com/u_15180952/4803751
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