我正在写一个高斯滤镜,我的目标是尽可能地匹配 Photoshop 中的高斯模糊滤镜。这是我的第一次图像处理尝试。我遇到的一些问题/问题是......
用我的滤镜进一步模糊图像会使它变暗,而 Photoshop 似乎会使它变亮。
我使用的偏差值(“sigma”,在我的代码中)是 r/3,这导致矩阵内的高斯曲线接近 0.0001……有没有更好的方法来确定这个值?
Photoshop(或大多数人)如何处理这种模糊的图像边框?
int matrixDimension = (radius*2)+1;
float sigma = radius/3;
float twoSigmaSquared = 2*pow(sigma, 2);
float oneOverSquareRootOfTwoPiSigmaSquared = 1/(sqrt(M_PI*twoSigmaSquared));
float kernel[matrixDimension];
int index = 0;
for (int offset = -radius; offset <= radius; offset++) {
float xSquared = pow(offset, 2);
float exponent = -(xSquared/twoSigmaSquared);
float eToThePower = pow(M_E, exponent);
float multFactor = oneOverSquareRootOfTwoPiSigmaSquared*eToThePower;
kernel[index] = multFactor;
index++;
}
//Normalize the kernel such that all its values will add to 1
float sum = 0;
for (int i = 0; i < matrixDimension; i++) {
sum += kernel[i];
}
for (int i = 0; i < matrixDimension; i++) {
kernel[i] = kernel[i]/sum;
}
//Blur horizontally
for (int row = 0; row < imageHeight; row++) {
for (int column = 0; column < imageWidth; column++) {
int currentPixel = (row*imageWidth)+column;
int sum1 = 0;
int sum2 = 0;
int sum3 = 0;
int sum4 = 0;
int index = 0;
for (int offset = -radius; offset <= radius; offset++) {
if (!(column+offset < 0) && !(column+offset > imageWidth-1)) {
int firstByteOfPixelWereLookingAtInSrcData = (currentPixel+offset)*4;
int in1 = srcData[firstByteOfPixelWereLookingAtInSrcData];
int in2 = srcData[firstByteOfPixelWereLookingAtInSrcData+1];
int in3 = srcData[firstByteOfPixelWereLookingAtInSrcData+2];
int in4 = srcData[firstByteOfPixelWereLookingAtInSrcData+3];
sum1 += (int)(in1 * kernel[index]);
sum2 += (int)(in2 * kernel[index]);
sum3 += (int)(in3 * kernel[index]);
sum4 += (int)(in4 * kernel[index]);
}
index++;
}
int currentPixelInData = currentPixel*4;
destData[currentPixelInData] = sum1;
destData[currentPixelInData+1] = sum2;
destData[currentPixelInData+2] = sum3;
destData[currentPixelInData+3] = sum4;
}
}
//Blur vertically
for (int row = 0; row < imageHeight; row++) {
for (int column = 0; column < imageWidth; column++) {
int currentPixel = (row*imageWidth)+column;
int sum1 = 0;
int sum2 = 0;
int sum3 = 0;
int sum4 = 0;
int index = 0;
for (int offset = -radius; offset <= radius; offset++) {
if (!(row+offset < 0) && !(row+offset > imageHeight-1)) {
int firstByteOfPixelWereLookingAtInSrcData = (currentPixel+(offset*imageWidth))*4;
int in1 = destData[firstByteOfPixelWereLookingAtInSrcData];
int in2 = destData[firstByteOfPixelWereLookingAtInSrcData+1];
int in3 = destData[firstByteOfPixelWereLookingAtInSrcData+2];
int in4 = destData[firstByteOfPixelWereLookingAtInSrcData+3];
sum1 += (int)(in1 * kernel[index]);
sum2 += (int)(in2 * kernel[index]);
sum3 += (int)(in3 * kernel[index]);
sum4 += (int)(in4 * kernel[index]);
}
index++;
}
int currentPixelInData = currentPixel*4;
finalData[currentPixelInData] = sum1;
finalData[currentPixelInData+1] = sum2;
finalData[currentPixelInData+2] = sum3;
finalData[currentPixelInData+3] = sum4;
}
}