Windows Mobile上实现图片任意角度旋转

Windows Mobile上实现图片任意角度旋转

作者：金海建

 

目的：在Windows Mobile上，微软的API和库不支持图片的任意角度旋转，只支持90,180,270度旋转。既然它不支持我们只能自力更生了。

简介：通过介绍和实现旋转PNG图片，来说明实现图片旋转的方法。过程大概如下，先用Imaging读取并解码png图片，使之转成ARGB格式的位图。然后利用顶点旋转的公式，对位图矩阵进行旋转，旋转完成后，利用Imaging库，转换成IImage接口。最后利用IImage接口来画图。

 

    先来看下平面直角坐标变换的旋转坐标变换,其定义是

定义：若二坐标系{O；i，j}和{O′；i′，j′}满足O≡O′，另∠（i，j′）=θ

        则坐标系{O′；i′，j′}可看成是由坐标系{O；i，j}绕O旋转θ角得到的，称由{O；i，j}到{O′；i′，j′}的变换为旋转坐标变换。

旋转公式为：

X' =  X cosθ -  Y sinθ

Y' =  X sinθ  + Y cosθ

由于我们是用数组的下表来表示坐标的，所以最小的坐标是为（0,0）。我们需要先做坐标旋转，然后平移坐标。如下图所示：

 

平移的动作，是把所以的负坐标变成正坐标。用MinX和MinY来表示最小的X坐标和Y坐标。

X' =  X cosθ -  Y sinθ - MinX;

Y' =  X sinθ  + Y cosθ - MinY;

根据上面的公式我们推出

x = (x'+MinX)cosθ+ (y'+MinY)sinθ

y = (y'+MinY)conθ- (x'+MinX)sinθ

 

图片旋转后，会出现失真现象，需要用双线性内插值进行优化

双线性内插值：对于一个目的像素，设置坐标通过反向变换得到的浮点坐标为(i+u,j+v)，其中i、j均为非负整数，u、v为[0,1)区间的浮点数，则这个像素得值 f(i+u,j+v) 可由原图像中坐标为 (i,j)、(i+1,j)、(i,j+1)、(i+1,j+1)所对应的周围四个像素的值决定，即：

f(i+u,j+v) = (1-u)(1-v)f(i,j) + (1-u)vf(i,j+1) + u(1-v)f(i+1,j) + uvf(i+1,j+1)

其中f(i,j)表示源图像(i,j)处的的像素值，以此类推。

这就是双线性内插值法。双线性内插值法计算量大，但缩放后图像质量高，不会出现像素值不连续的的情况。由于双线性插值具有低通滤波器的性质，使高频分量受损，所以可能会使图像轮廓在一定程度上变得模糊。

 

 

旋转代码

 void RotateImageBuf(const BYTE* src, int srcWidth, int srcHeight, BYTE*& dst, int& dstWidth, int& dstHeight, double angle) { double cosA = cos(angle); double sinA = sin(angle); double x1 = srcWidth * cosA; double y1 = srcWidth * sinA; double x2 = srcWidth * cosA - srcHeight * sinA; double y2 = srcWidth * sinA + srcHeight * cosA; double x3 = - srcHeight * sinA; double y3 = srcHeight * cosA; double minWidth = min(0,min(x3,min(x1,x2))); double minHeight = min(0,min(y3,min(y1,y2))); double maxWidth = max(0,max(x3,max(x1,x2))); double maxHeight = max(0,max(y3,max(y1,y2))); dstWidth = abs(maxWidth - minWidth) + 1; dstHeight = abs(maxHeight - minHeight) + 1; double ndstX = 0; double ndstY = 0; dst = new BYTE[dstWidth * dstHeight * 4]; UINT32 *pDst = (UINT32 *)dst; UINT32 *pSrc = (UINT32 *)src; UINT32 crDefault = ((UINT32 *)src)[0]; UINT32 color [2][2]; BYTE alpha[2][2]; BYTE rColor[2][2]; BYTE gColor[2][2]; BYTE bColor[2][2]; BYTE afinal,rfinal,gfinal,bfinal; double ox,oy; for(int y=0; y < dstHeight; y++) { for(int x=0; x < dstWidth; x++) { ndstX = (x + minWidth) * cosA + (y + minHeight) * sinA; ndstY = (y + minHeight) * cosA - (x +minWidth) * sinA; if((ndstX >= 0) && (ndstX < srcWidth) && (ndstY >= 0) && (ndstY < srcHeight)) { color[0][0] = pSrc[ (int)((int)ndstY*srcWidth + ndstX) ]; if((int)ndstX + 1 >= srcWidth) color[1][0] = crDefault; else color[1][0] = pSrc[ (int)((int)ndstY*srcWidth + ndstX +1) ]; if((int)ndstY + 1 >= srcHeight) color[0][1] = crDefault; else color[0][1] = pSrc[ (int)(((int)ndstY+1)*srcWidth + ndstX) ]; if((int)ndstY + 1 >= srcHeight || (int)ndstX + 1 >= srcWidth) color[1][1] = crDefault; else color[1][1] = pSrc[ (int)(((int)ndstY+1)*srcWidth + ndstX+1) ]; alpha[0][0] = (color[0][0] & 0XFF000000) >> 24; bColor[0][0] = (color[0][0] & 0XFF0000) >> 16; gColor[0][0] = (color[0][0] & 0X00FF00) >> 8; rColor[0][0] = color[0][0] & 0X0000FF; alpha[1][0] = (color[1][0] & 0XFF000000) >> 24; bColor[1][0] = (color[1][0] & 0XFF0000) >> 16; gColor[1][0] = (color[1][0] & 0X00FF00) >> 8; rColor[1][0] = color[1][0] & 0X0000FF; alpha[0][1] = (color[0][1] & 0XFF000000) >> 24; bColor[0][1] = (color[0][1] & 0XFF0000) >> 16; gColor[0][1] = (color[0][1] & 0X00FF00) >> 8; rColor[0][1] = color[0][1] & 0X0000FF; alpha[1][1] = (color[1][1] & 0XFF000000) >> 24; bColor[1][1] = (color[1][1] & 0XFF0000) >> 16; gColor[1][1] = (color[1][1] & 0X00FF00) >> 8; rColor[1][1] = color[1][1] & 0X0000FF; //f(i+u,j+v) = (1-u)(1-v)f(i,j) + (1-u)vf(i,j+1) + u(1-v)f(i+1,j) + uvf(i+1,j+1) ox = (ndstX - (int)ndstX); oy = (ndstY - (int)ndstY); rfinal = (1 - ox)*(1 - oy)*rColor[0][0] + ox*(1 - oy)*rColor[1][0] + (1-ox)*oy*rColor[0][1] + ox*oy*rColor[1][1]; gfinal = (1 - ox)*(1 - oy)*gColor[0][0] + ox*(1 - oy)*gColor[1][0] + (1-ox)*oy*gColor[0][1] + ox*oy*gColor[1][1]; bfinal = (1 - ox)*(1 - oy)*bColor[0][0] + ox*(1 - oy)*bColor[1][0] + (1-ox)*oy*bColor[0][1] + ox*oy*bColor[1][1]; afinal = (1 - ox)*(1 - oy)*alpha[0][0] + ox*(1 - oy)*alpha[1][0] + (1-ox)*oy*alpha[0][1] + ox*oy*alpha[1][1]; pDst[y * (int)dstWidth + x] = RGBA(rfinal,gfinal,bfinal,afinal); } else { pDst[y * (int)dstWidth + x] = crDefault; } } } }

 

需要对浮点型运算，改为整形预算。在模拟上测试过，旋转一张图片，整形预算要比浮点型预算快20倍。

改为整形运算代码。

void RotateImageZhenxingBuf(const BYTE* src, int srcWidth, int srcHeight, BYTE*& dst, int& dstWidth, int& dstHeight, double angle) { double cosA = cos(angle); double sinA = sin(angle); double x1 = srcWidth * cosA; double y1 = srcWidth * sinA; double x2 = srcWidth * cosA - srcHeight * sinA; double y2 = srcWidth * sinA + srcHeight * cosA; double x3 = - srcHeight * sinA; double y3 = srcHeight * cosA; double minWidthD = min(0,min(x3,min(x1,x2))); double minHeightD = min(0,min(y3,min(y1,y2))); double maxWidthD = max(0,max(x3,max(x1,x2))); double maxHeightD = max(0,max(y3,max(y1,y2))); dstWidth = abs(minWidthD - maxWidthD) + 1; dstHeight = abs(maxHeightD - minHeightD) + 1; int minWidth= minWidthD; int minHeight= minHeightD; int maxWidth = maxWidthD; int maxHeight = maxHeightD; int ndstX = 0; int ndstY = 0; dst = new BYTE[dstWidth * dstHeight * 4]; UINT32 *pDst = (UINT32 *)dst; UINT32 *pSrc = (UINT32 *)src; UINT32 crDefault = ((UINT32 *)src)[0]; UINT32 color [2][2]; BYTE alpha[2][2]; BYTE rColor[2][2]; BYTE gColor[2][2]; BYTE bColor[2][2]; int afinal,rfinal,gfinal,bfinal; long icosA = cosA * 256 * 256; long isinA = sinA * 256 * 256; int x; int y; int kx; int ky; for(int j=0; j < dstHeight; j++) { for(int i=0; i < dstWidth; i++) { ndstX = (i + minWidth) * icosA + (j + minHeight) * isinA; ndstY = (j + minHeight) * icosA - (i +minWidth) * isinA; ndstX = ndstX >> 8; ndstY = ndstY >> 8; if ( (ndstX >> 8) < srcWidth && (ndstX >> 8) >=0 && (ndstY >> 8) < srcHeight && (ndstY >> 8) >= 0) { kx = ndstX >> 8; ky = ndstY >> 8; x = ndstX & 0xFF; y = ndstY & 0xFF; color[0][0] = pSrc[ ky*srcWidth + kx ]; if(kx + 1 >= srcWidth) color[1][0] = crDefault; else color[1][0] = pSrc[ ky*srcWidth + kx +1 ]; if(ky + 1 >= srcHeight) color[0][1] = crDefault; else color[0][1] = pSrc[ (ky+1)*srcWidth + kx ]; if(ky + 1 >= srcHeight || kx + 1 >= srcWidth) color[1][1] = crDefault; else color[1][1] = pSrc[ (ky+1)*srcWidth + kx+1 ]; alpha[0][0] = (color[0][0] & 0XFF000000) >> 24; bColor[0][0] = (color[0][0] & 0XFF0000) >> 16; gColor[0][0] = (color[0][0] & 0X00FF00) >> 8; rColor[0][0] = color[0][0] & 0XFF; alpha[1][0] = (color[1][0] & 0XFF000000) >> 24; bColor[1][0] = (color[1][0] & 0XFF0000) >> 16; gColor[1][0] = (color[1][0] & 0X00FF00) >> 8; rColor[1][0] = color[1][0] & 0XFF; alpha[0][1] = (color[0][1] & 0XFF000000) >> 24; bColor[0][1] = (color[0][1] & 0XFF0000) >> 16; gColor[0][1] = (color[0][1] & 0X00FF00) >> 8; rColor[0][1] = color[0][1] & 0XFF; alpha[1][1] = (color[1][1] & 0XFF000000) >> 24; bColor[1][1] = (color[1][1] & 0XFF0000) >> 16; gColor[1][1] = (color[1][1] & 0X00FF00) >> 8; rColor[1][1] = color[1][1] & 0XFF; afinal = (0x100 - x)*(0x100 - y)*alpha[0][0] + x*(0x100 - y)*alpha[1][0] + (0x100-x)*y*alpha[0][1] + x*y*alpha[1][1]; rfinal = (0x100 - x)*(0x100 - y)*rColor[0][0] + x*(0x100 - y)*rColor[1][0] + (0x100-x)*y*rColor[0][1] + x*y*rColor[1][1]; gfinal = (0x100 - x)*(0x100 - y)*gColor[0][0] + x*(0x100 - y)*gColor[1][0] + (0x100-x)*y*gColor[0][1] + x*y*gColor[1][1]; bfinal = (0x100 - x)*(0x100 - y)*bColor[0][0] + x*(0x100 - y)*bColor[1][0] + (0x100-x)*y*bColor[0][1] + x*y*bColor[1][1]; afinal = afinal >> 16; if (afinal>255) afinal = 255; if (afinal<0) afinal = 0; rfinal = rfinal >> 16; if (rfinal>255) rfinal = 255; if (rfinal<0) rfinal = 0; gfinal = gfinal >> 16; if (gfinal>255) gfinal = 255; if (gfinal<0) gfinal = 0; bfinal = bfinal >> 16; if (bfinal>255) bfinal = 255; if (bfinal<0) bfinal = 0; pDst[j * dstWidth + i] = RGBA(rfinal,gfinal,bfinal,afinal); } else { pDst[j * dstWidth + i] = crDefault; } } } }

 

用Imaging接口加载png图片，并调用RotateImageBuf进行旋转，最后返回IImage接口。

// need to delete pImagebuf; HRESULT RotateImage(IImagingFactory *pImgFactory, IImage *pImage, IImage * &pImageOut, LPBYTE &pImageBuf, double angle) { HRESULT hr = S_OK; IBitmapImage *pIBitmap = NULL; ImageInfo ImInfo; pImage->GetImageInfo(&ImInfo); if((ImInfo.PixelFormat & 0xFF00)>>8 != 32) { hr = S_FALSE; goto Error; } if(S_OK != pImgFactory->CreateBitmapFromImage( pImage, ImInfo.Width, ImInfo.Height, ImInfo.PixelFormat, InterpolationHintDefault, &pIBitmap)) { hr = S_FALSE; goto Error; } RECT rcLocked ={0,0,ImInfo.Width,ImInfo.Height}; BitmapData bmpData; if(S_OK != pIBitmap->LockBits(&rcLocked, ImageLockModeRead | ImageLockModeWrite, ImInfo.PixelFormat, &bmpData)) { hr = S_FALSE; goto Error; } BYTE *pDst = NULL; int nDstWidth=0,nDstHeight=0; RotateImageZhenxingBuf((BYTE *)bmpData.Scan0, ImInfo.Width, ImInfo.Height, pDst, nDstWidth, nDstHeight, angle); pIBitmap->UnlockBits(&bmpData); BitmapData bmpDataNew; bmpDataNew.Height = nDstHeight; bmpDataNew.Width = nDstWidth; bmpDataNew.PixelFormat = ImInfo.PixelFormat; bmpDataNew.Stride = nDstWidth * 4; bmpDataNew.Reserved = 0; bmpDataNew.Scan0 = (void *)pDst; IBitmapImage *pBmpImageNew = NULL; hr = pImgFactory->CreateBitmapFromBuffer(&bmpDataNew, &pBmpImageNew); IImage * pImageNew = NULL; pBmpImageNew->QueryInterface(IID_IImage, (void **)&pImageNew); pImageOut = pImageNew; pImageBuf = pDst; Error: if(pBmpImageNew) pBmpImageNew->Release(); if(pIBitmap) pIBitmap->Release(); return hr; }