(rt #124001) avoid flooring a second time in matrix transform interpolation

[imager.git] / rotate.im

diff --git a/rotate.im b/rotate.im
index 861810d48c5ab308b62291166252570e9532f352..96981be7ae6030a0f2279ded3849e5d97c0a40e9 100644 (file)
--- a/rotate.im
+++ b/rotate.im
@@ -130,7 +130,6 @@ static i_color interp_i_color(i_color before, i_color after, double pos,
   i_color out;
   int ch;
 
-  pos -= floor(pos);
   if (channels == 1 || channels == 3) {
     for (ch = 0; ch < channels; ++ch)
       out.channel[ch] = ((1-pos) * before.channel[ch] + pos * after.channel[ch]) + 0.5;
@@ -152,6 +151,10 @@ static i_color interp_i_color(i_color before, i_color after, double pos,
        out.channel[ch] = I_LIMIT_8(out_level);
       }
     }
+    else {
+      for (ch = 0; ch < channels-1; ++ch)
+       out.channel[ch] = 0;
+    }
 
     out.channel[channels-1] = total_cover;
   }
@@ -166,7 +169,6 @@ static i_fcolor interp_i_fcolor(i_fcolor before, i_fcolor after, double pos,
   i_fcolor out;
   int ch;
 
-  pos -= floor(pos);
   if (channels == 1 || channels == 3) {
     for (ch = 0; ch < channels; ++ch)
       out.channel[ch] = (1-pos) * before.channel[ch] + pos * after.channel[ch];
@@ -188,6 +190,10 @@ static i_fcolor interp_i_fcolor(i_fcolor before, i_fcolor after, double pos,
        out.channel[ch] = I_LIMIT_DOUBLE(out_level);
       }
     }
+    else {
+      for (ch = 0; ch < channels-1; ++ch)
+       out.channel[ch] = 0;
+    }
 
     out.channel[channels-1] = total_cover;
   }
@@ -252,22 +258,26 @@ i_img *i_matrix_transform_bg(i_img *src, i_img_dim xsize, i_img_dim ysize, const
        if (fabs(sz) > 0.0000001 
            && sx >= -1 && sx < src->xsize
            && sy >= -1 && sy < src->ysize) {
-         i_img_dim bx = floor(sx);
-         i_img_dim by = floor(sy);
+         double fsx = floor(sx);
+         double fsy = floor(sy);
+         i_img_dim bx = fsx;
+         i_img_dim by = fsy;
 
          ROT_DEBUG(fprintf(stderr, "map " i_DFp " to %g,%g\n", i_DFcp(x, y), sx, sy));
-         if (sx != bx) {
-           if (sy != by) {
+         if (sx != fsx) {
+           double dx = sx - fsx;
+           if (sy != fsy) {
              IM_COLOR c[2][2]; 
              IM_COLOR ci2[2];
+             double dy = sy - fsy;
              ROT_DEBUG(fprintf(stderr, " both non-int\n"));
              for (i = 0; i < 2; ++i)
                for (j = 0; j < 2; ++j)
                  if (IM_GPIX(src, bx+i, by+j, &c[j][i]))
                    c[j][i] = back;
              for (j = 0; j < 2; ++j)
-               ci2[j] = interp_i_color(c[j][0], c[j][1], sx, src->channels);
-             vals[x] = interp_i_color(ci2[0], ci2[1], sy, src->channels);
+               ci2[j] = interp_i_color(c[j][0], c[j][1], dx, src->channels);
+             vals[x] = interp_i_color(ci2[0], ci2[1], dy, src->channels);
            }
            else {
              IM_COLOR ci2[2];
@@ -275,22 +285,23 @@ i_img *i_matrix_transform_bg(i_img *src, i_img_dim xsize, i_img_dim ysize, const
              for (i = 0; i < 2; ++i)
                if (IM_GPIX(src, bx+i, sy, ci2+i))
                  ci2[i] = back;
-             vals[x] = interp_i_color(ci2[0], ci2[1], sx, src->channels);
+             vals[x] = interp_i_color(ci2[0], ci2[1], dx, src->channels);
            }
          }
          else {
-           if (sy != (i_img_dim)sy) {
+           if (sy != fsy) {
              IM_COLOR ci2[2];
+             double dy = sy - fsy;
              ROT_DEBUG(fprintf(stderr, " x int, y non-int\n"));
              for (i = 0; i < 2; ++i)
                if (IM_GPIX(src, bx, by+i, ci2+i))
                  ci2[i] = back;
-             vals[x] = interp_i_color(ci2[0], ci2[1], sy, src->channels);
+             vals[x] = interp_i_color(ci2[0], ci2[1], dy, src->channels);
            }
            else {
              ROT_DEBUG(fprintf(stderr, " both int\n"));
              /* all the world's an integer */
-             if (IM_GPIX(src, sx, sy, vals+x))
+             if (IM_GPIX(src, bx, by, vals+x))
                vals[x] = back;
            }
          }