/******************* TO DO 4 *********************
* AccumulateBlend:
* INPUT:
* img: a new image to be added to acc
* acc: portion of the accumulated image where img is to be added
* M: translation matrix for calculating a bounding box
* blendWidth: width of the blending function (horizontal hat function;
* try other blending functions for extra credit)
* OUTPUT:
* add a weighted copy of img to the subimage specified in acc
* the first 3 band of acc records the weighted sum of pixel colors
* the fourth band of acc records the sum of weight
*/
static void AccumulateBlend(CByteImage& img, CFloatImage& acc, CTransform3x3 M, float blendWidth)
{
/* Compute the bounding box of the image of the image */
int bb_min_x, bb_min_y, bb_max_x, bb_max_y;
ImageBoundingBox(img, M, bb_min_x, bb_min_y, bb_max_x, bb_max_y);
int imgWidth = img.Shape().width;
int imgHeight = img.Shape().height;
CTransform3x3 Minv = M.Inverse();
for (int y = bb_min_y; y <= bb_max_y; y++) {
for (int x = bb_min_x; x < bb_max_x; x++) {
/* Check bounds in destination */
if (x < 0 || x >= acc.Shape().width ||
y < 0 || y >= acc.Shape().height)
continue;
/* Compute source pixel and check bounds in source */
CVector3 p_dest, p_src;
p_dest[0] = x;
p_dest[1] = y;
p_dest[2] = 1.0;
p_src = Minv * p_dest;
float x_src = (float) (p_src[0] / p_src[2]);
float y_src = (float) (p_src[1] / p_src[2]);
if (x_src < 0.0 || x_src >= img.Shape().width - 1 ||
y_src < 0.0 || y_src >= img.Shape().height - 1)
continue;
int xf = (int) floor(x_src);
int yf = (int) floor(y_src);
int xc = xf + 1;
int yc = yf + 1;
/* Skip black pixels */
if (img.Pixel(xf, yf, 0) == 0x0 &&
img.Pixel(xf, yf, 1) == 0x0 &&
img.Pixel(xf, yf, 2) == 0x0)
continue;
if (img.Pixel(xc, yf, 0) == 0x0 &&
img.Pixel(xc, yf, 1) == 0x0 &&
img.Pixel(xc, yf, 2) == 0x0)
continue;
if (img.Pixel(xf, yc, 0) == 0x0 &&
img.Pixel(xf, yc, 1) == 0x0 &&
img.Pixel(xf, yc, 2) == 0x0)
continue;
if (img.Pixel(xc, yc, 0) == 0x0 &&
img.Pixel(xc, yc, 1) == 0x0 &&
img.Pixel(xc, yc, 2) == 0x0)
continue;
double weight = 1.0;
// *** BEGIN TODO ***
// set weight properly
//(see mosaics lecture slide on "feathering") P455 on notebook
//Q：How to find the invalid distance ? ->
double distance = ((imgWidth - x - 1)*(imgWidth - x - 1) + (imgHeight - y - 1)*(imgHeight - y - 1));
if (distance < blendWidth)
{
weight = distance / blendWidth;
}
// *** END TODO ***
acc.Pixel(x, y, 0) += (float) (weight * img.PixelLerp(x_src, y_src, 0));
acc.Pixel(x, y, 1) += (float) (weight * img.PixelLerp(x_src, y_src, 1));
acc.Pixel(x, y, 2) += (float) (weight * img.PixelLerp(x_src, y_src, 2));
acc.Pixel(x, y, 3) += (float) weight;
}
}
}
/******************* TO DO *********************
* AccumulateBlend:
* INPUT:
* img: a new image to be added to acc
* acc: portion of the accumulated image where img is to be added
* M: the transformation mapping the input image 'img' into the output panorama 'acc'
* blendWidth: width of the blending function (horizontal hat function;
* try other blending functions for extra credit)
* OUTPUT:
* add a weighted copy of img to the subimage specified in acc
* the first 3 band of acc records the weighted sum of pixel colors
* the fourth band of acc records the sum of weight
*/
static void AccumulateBlend(CByteImage& img, CFloatImage& acc, CTransform3x3 M, float blendWidth)
{
// BEGIN TODO
// Fill in this routine
// get shape of acc and img
CShape sh = img.Shape();
int width = sh.width;
int height = sh.height;
CShape shacc = acc.Shape();
int widthacc = shacc.width;
int heightacc = shacc.height;
// get the bounding box of img in acc
int min_x, min_y, max_x, max_y;
ImageBoundingBox(img, M, min_x, min_y, max_x, max_y);
CVector3 p;
double newx, newy;
// Exposure Compensation
double lumaScale = 1.0;
double lumaAcc = 0.0;
double lumaImg = 0.0;
int cnt = 0;
for (int ii = min_x; ii < max_x; ii++)
for (int jj = min_y; jj < max_y; jj++)
{
// flag: current pixel black or not
bool flag = false;
p[0] = ii; p[1] = jj; p[2] = 1;
p = M.Inverse() * p;
newx = p[0] / p[2];
newy = p[1] / p[2];
// If in the overlapping region
if (newx >=0 && newx < width && newy >=0 && newy < height)
{
if (acc.Pixel(ii,jj,0) == 0 &&
acc.Pixel(ii,jj,1) == 0 &&
acc.Pixel(ii,jj,2) == 0)
flag = true;
if (img.PixelLerp(newx,newy,0) == 0 &&
img.PixelLerp(newx,newy,1) == 0 &&
img.PixelLerp(newx,newy,2) == 0)
flag = true;
if (!flag)
{
// Compute Y using RGB (RGB -> YUV)
lumaAcc = 0.299 * acc.Pixel(ii,jj,0) +
0.587 * acc.Pixel(ii,jj,1) +
0.114 * acc.Pixel(ii,jj,2);
lumaImg = 0.299 * img.PixelLerp(newx,newy,0) +
0.587 * img.PixelLerp(newx,newy,1) +
0.114 * img.PixelLerp(newx,newy,2);
if (lumaImg != 0)
{
double scale = lumaAcc / lumaImg;
if (scale > 0.5 && scale < 2)
{
lumaScale += lumaAcc / lumaImg;
cnt++;
}
}
}
}
}
if (cnt != 0)
lumaScale = lumaScale / (double)cnt;
else lumaScale = 1.0;
// add every pixel in img to acc, feather the region withing blendwidth to the bounding box,
// pure black pixels (caused by warping) are not added
double weight;
for (int ii = min_x; ii < max_x; ii++)
for (int jj = min_y; jj < max_y; jj++)
{
p[0] = ii; p[1] = jj; p[2] = 1;
p = M.Inverse() * p;
newx = p[0] / p[2];
newy = p[1] / p[2];
if ((newx >= 0) && (newx < width-1) && (newy >= 0) && (newy < height-1))
{
weight = 1.0;
if ( (ii >= min_x) && (ii < (min_x+blendWidth)) )
weight = (ii-min_x) / blendWidth;
if ( (ii <= max_x) && (ii > (max_x-blendWidth)) )
weight = (max_x-ii) / blendWidth;
if (img.Pixel(iround(newx),iround(newy),0) == 0 &&
img.Pixel(iround(newx),iround(newy),1) == 0 &&
img.Pixel(iround(newx),iround(newy),2) == 0)
weight = 0.0;
double LerpR = img.PixelLerp(newx, newy, 0);
double LerpG = img.PixelLerp(newx, newy, 1);
double LerpB = img.PixelLerp(newx, newy, 2);
double r = LerpR*lumaScale > 255.0 ? 255.0 : LerpR*lumaScale;
double g = LerpG*lumaScale > 255.0 ? 255.0 : LerpG*lumaScale;
double b = LerpB*lumaScale > 255.0 ? 255.0 : LerpB*lumaScale;
acc.Pixel(ii,jj,0) += r * weight;
acc.Pixel(ii,jj,1) += g * weight;
acc.Pixel(ii,jj,2) += b * weight;
acc.Pixel(ii,jj,3) += weight;
}
}
printf("AccumulateBlend\n");
// END TODO
}