编程图像比较

时间:2012-10-03 10:46:20

标签: c# gdi+ gdi

我尝试比较2张图片。为此我使用2个PreentScreens一个接一个地做(这是理想的)。当我使用像素比较来比较这个屏幕时:

public static CompareResult Compare(Bitmap bmp1, Bitmap bmp2)
{
    CompareResult cr = CompareResult.ciCompareOk;

    if (bmp1.Size != bmp2.Size)
    {
        cr = CompareResult.ciSizeMismatch;
    }
    else
    {
        for (int x = 0; x < bmp1.Width 
             && cr == CompareResult.ciCompareOk; x++)
        {
            for (int y = 0; y < bmp1.Height 
                         && cr == CompareResult.ciCompareOk; y++)
            {
                if (bmp1.GetPixel(x, y) != bmp2.GetPixel(x, y))
                    cr = CompareResult.ciPixelMismatch;
            }
        }
    }
    return cr;
}

我得到的结果是正确的 - 比较是相同的,但是需要花费很多时间,当我尝试哈希这个位图并比较它的值时 - 我得到了错误的结果。当我将图像与自身进行比较时 - 一切正常。有什么不对?这是哈希比较的代码:

public enum CompareResult
        {
            ciCompareOk,
            ciPixelMismatch,
            ciSizeMismatch
        };

        public static CompareResult Compare(Bitmap bmp1, Bitmap bmp2)
        {
            CompareResult cr = CompareResult.ciCompareOk;

            //Test to see if we have the same size of image
            if (bmp1.Size != bmp2.Size)
            {
                cr = CompareResult.ciSizeMismatch;
            }
            else
            {
                //Convert each image to a byte array
                System.Drawing.ImageConverter ic = 
                       new System.Drawing.ImageConverter();
                byte[] btImage1 = new byte[1];
                btImage1 = (byte[])ic.ConvertTo(bmp1, btImage1.GetType());
                byte[] btImage2 = new byte[1];
                btImage2 = (byte[])ic.ConvertTo(bmp2, btImage2.GetType());

                //Compute a hash for each image
                SHA256Managed shaM = new SHA256Managed();
                byte[] hash1 = shaM.ComputeHash(btImage1);
                byte[] hash2 = shaM.ComputeHash(btImage2);

                //Compare the hash values
                for (int i = 0; i < hash1.Length && i < hash2.Length 
                                  && cr == CompareResult.ciCompareOk; i++)
                {
                    if (hash1[i] != hash2[i])
                        cr = CompareResult.ciPixelMismatch;
                }
            }
            return cr;
        }

1 个答案:

答案 0 :(得分:1)

包含示例代码的How to compare Image objects with C# .NET?的可能重复。

另一个有用的链接是Dominic Green的this博客文章。代码有点小,使用Base64散列而不是SHA256散列。这明显更快,但你应该知道比较图像不是轻微的操作。

但回到问题本身,你有多确定两张图片都是平等的?是否可能两个图像之间可能存在细微差别?您的鼠标光标移动,时钟显示更新,...