C# 图像处理-缩略图的自动调整/裁剪

我用这个撞到了砖墙。。。我知道我在逻辑上有缺陷，但我会解释我现在的处境

我正在（尝试）编写代码，为Silverlight应用程序底部的导航栏动态创建一个正方形（75x75）像素缩略图。 当我调试下面的代码时，在缩放嵌套循环的过程中，我会不断得到一个“数组索引越界”错误 （我只调试过srcWidth>srcHeight，一次一步）

我测试的源图像是307x162（49734像素） 此操作的dest大小（每个当前逻辑）为150x75（11250像素） 当然，在此之后，我打算将结果裁剪到75x75

在点击11251作为目标的索引之前，它只通过了源图像的一半。 我知道这是我的逻辑， 我只是不知道我用来建造目的地的尺寸是否有问题， 或者在将浮点数转换为整数的近似值中， 或者两者都不是

我不知道，这就是我在这里发帖的原因。。。无论如何，这是我的消息来源：

    private void ResizeNavBarImage(Image src)
    {
        const int SizeOfRGB = 4;
        WriteableBitmap bmpSource = new WriteableBitmap((BitmapSource)src.Source);
        int[] iSourcePixels = bmpSource.Pixels;
        int srcWidth = bmpSource.PixelWidth;
        int srcHeight = bmpSource.PixelHeight;

        int destWidth = 75;
        int destHeight = 75;

        float xFactor = srcWidth / destWidth;
        float yFactor = srcHeight / destHeight;

        float xSource, ySource;
        int iApprox;
        int iIndex = 0;

        if (srcWidth > srcHeight)
        {
            WriteableBitmap bmpDest = new WriteableBitmap((int)(destWidth * yFactor), destHeight);
            int[] iDestPixels = bmpDest.Pixels;

            // Resize srcHeight to destHeight, srcWidth to same ratio
            for (int i = 0; i < srcHeight; i++)
            {
                for (int j = 0; j < srcWidth; j++)
                {
                    xSource = j * yFactor;
                    ySource = i * yFactor;
                    iApprox = (int)(ySource * srcWidth + xSource);
                    iDestPixels[iIndex++] = iSourcePixels[iApprox];
                }
            }

            // Crop half of difference from each side of the width
            srcWidth = bmpDest.PixelWidth;
            srcHeight = bmpDest.PixelHeight;
            int xLeftOffset = (srcWidth - srcHeight) / 2;

            WriteableBitmap bmpFinalDest = new WriteableBitmap(destWidth, destHeight);
            for (int iPixelRow = 0; iPixelRow < destHeight; iPixelRow++)
            {
                int srcOffset = (iPixelRow * srcWidth + xLeftOffset) * SizeOfRGB;
                int destOffset = iPixelRow * destWidth * SizeOfRGB;
                Buffer.BlockCopy(bmpDest.Pixels, srcOffset, bmpFinalDest.Pixels, destOffset, destWidth * SizeOfRGB);
            }

            src.Source = (ImageSource)bmpFinalDest;
        }
        else if (srcWidth < srcHeight)
        {
            WriteableBitmap bmpDest = new WriteableBitmap(destWidth, (int)(destHeight * xFactor));
            int[] iDestPixels = bmpDest.Pixels;

            // Resize srcWidth to destWidth, srcHeight to same ratio
            for (int i = 0; i < srcHeight; i++)
            {
                for (int j = 0; j < srcWidth; j++)
                {
                    xSource = j * xFactor;
                    ySource = i * xFactor;
                    iApprox = (int)(ySource * srcWidth + xSource);
                    iDestPixels[iIndex++] = iSourcePixels[iApprox];
                }
            }

            // Crop half of difference from each side of the height
            srcWidth = bmpDest.PixelWidth;
            srcHeight = bmpDest.PixelHeight;
            int yTopOffset = (srcHeight - srcWidth) / 2;

            WriteableBitmap bmpFinalDest = new WriteableBitmap(destWidth, destHeight);
            for (int iPixelRow = yTopOffset; iPixelRow < (destHeight - (yTopOffset * 2)); iPixelRow++)
            {
                int srcOffset = iPixelRow * srcWidth * SizeOfRGB;
                int destOffset = iPixelRow * destWidth * SizeOfRGB;
                Buffer.BlockCopy(bmpDest.Pixels, srcOffset, bmpFinalDest.Pixels, destOffset, destWidth * SizeOfRGB);
            }

            src.Source = (ImageSource)bmpFinalDest;
        }
        else // (srcWidth == srcHeight)
        {
            WriteableBitmap bmpDest = new WriteableBitmap(destWidth, destHeight);
            int[] iDestPixels = bmpDest.Pixels;

            // Resize and set source
            for (var i = 0; i < srcHeight; i++)
            {
                for (var j = 0; j < srcWidth; j++)
                {
                    xSource = j * xFactor;
                    ySource = i * yFactor;
                    iApprox = (int)(ySource * srcWidth + xSource);
                    iDestPixels[iIndex++] = iSourcePixels[iApprox];
                }
            }
            src.Source = (ImageSource)bmpDest;
        }
    }

private void ResizeNavBarImage（图像src）
{
常数int SizeOfRGB=4；
WriteableBitmap bmpSource=新的WriteableBitmap（（位图源）src.Source）；
int[]iSourcePixels=bmpSource.Pixels；
int srcWidth=bmpSource.PixelWidth；
int srchheight=bmpSource.PixelHeight；
宽度=75；
高度=75；
float xFactor=srcWidth/destWidth；
float yFactor=srcHeight/destHeight；
浮动xSource、ySource；
int iApprox；
国际指数=0；
如果（srcWidth>srcHeight）
{
WriteableBitmap bmpDest=新的WriteableBitmap（（int）（destWidth*yFactor），destHeight）；
int[]iDestPixels=bmpDest.Pixels；
//将srcHeight调整为destHeight，srcWidth调整为相同比率
对于（int i=0；i

===============================================================================

以下是我为子孙后代编写的工作代码（带有WriteableBitmapEx）：

    private void ResizeNavBarImage(Image src)
    {
        WriteableBitmap bmpSource = new WriteableBitmap((BitmapSource)src.Source);
        int srcWidth = bmpSource.PixelWidth;
        int srcHeight = bmpSource.PixelHeight;

        int finalDestWidth = 75;
        int finalDestHeight = 75;

        // Resize
        float xFactor = ((float)finalDestWidth / (float)srcWidth);
        float yFactor = ((float)finalDestHeight / (float)srcHeight);
        float Factor = 0;

        if (xFactor < yFactor)
            Factor = yFactor;
        else
            Factor = xFactor;

        int destWidth = (int)(srcWidth * Factor);
        int destHeight = (int)(srcHeight * Factor);

        if (destWidth < destHeight && destWidth != finalDestWidth)
            destWidth = finalDestWidth;
        else if (destWidth > destHeight && destHeight != finalDestHeight)
            destHeight = finalDestHeight;

        WriteableBitmap bmpDest = bmpSource.Resize(destWidth, destHeight, WriteableBitmapExtensions.Interpolation.Bilinear);

        // Crop
        int Offset;
        WriteableBitmap bmpFinalDest = new WriteableBitmap(finalDestWidth, finalDestHeight);

        if (destWidth > destHeight)
        {
            Offset = (bmpDest.PixelWidth - bmpDest.PixelHeight) / 2;
            if (finalDestWidth % 2 != 0 && Offset % 2 == 0)
                Offset -= 1;
            bmpFinalDest = bmpDest.Crop(Offset, 0, finalDestWidth, finalDestHeight);
        }
        else if (destWidth < destHeight)
        {
            Offset = (bmpDest.PixelHeight - bmpDest.PixelWidth) / 2;
            if (finalDestHeight % 2 != 0 && Offset % 2 == 0)
                Offset -= 1;
            bmpFinalDest = bmpDest.Crop(0, Offset, finalDestWidth, finalDestHeight);
        }
        else
            bmpFinalDest = bmpDest;

        src.Source = (ImageSource)bmpFinalDest;
    }

private void ResizeNavBarImage（图像src）
{
WriteableBitmap bmpSource=新的WriteableBitmap（（位图源）src.Source）；
int srcWidth=bmpSource.PixelWidth；
int srchheight=bmpSource.PixelHeight；
int finalDestWidth=75；
int finalDestHeight=75；
//调整大小
float xFactor=（（float）finalestwidth/（float）srcWidth）；
浮动Y因子=（（浮动）最终高度/（浮动）高度）；
浮动系数=0；
if（xFactorWriteableBitmap wb = new WriteableBitmap(src, new ScaleTransform() { ScaleX = 0.25, ScaleY = 0.25 });
wb.Invalidate();
src.Source = wb;