From d755f217a3a920eb58ce598e650111457351ceba Mon Sep 17 00:00:00 2001
From: giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8>
Date: Sat, 10 Dec 2011 03:07:44 +0000
Subject: Fix always black output with resampling

git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@1605 9d0c8265-081b-0410-96cb-a4ca84ce46f8
---
 editor/pamscale.c | 45 +++++++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 20 deletions(-)

(limited to 'editor/pamscale.c')

diff --git a/editor/pamscale.c b/editor/pamscale.c
index 8a2fac6a..c59d4ebc 100644
--- a/editor/pamscale.c
+++ b/editor/pamscale.c
@@ -968,8 +968,8 @@ appendWeight(WLIST * const WList,
 
 
 static sample
-floatToSample(double const value,
-              sample const maxval) {
+unnormalize(double const normalized,
+            sample const maxval) {
 
     /* Take care here, the conversion of any floating point value <=
        -1.0 to an unsigned type is _undefined_.  See ISO 9899:1999
@@ -980,7 +980,7 @@ floatToSample(double const value,
        weights.  
     */
 
-    return MIN(maxval, (sample)(MAX(0.0, (value + 0.5))));
+    return MIN(maxval, (sample)(MAX(0.0, (normalized*maxval + 0.5))));
 }
 
 
@@ -1313,8 +1313,9 @@ addInPixel(const struct pam * const pamP,
            unsigned int       const opacityPlane,
            double *           const accum) {
 /*----------------------------------------------------------------------------
-  Add into *accum the values from the tuple 'tuple', weighted by
-  'weight'.
+  Add into accum[] the values from the tuple 'tuple', weighted by 'weight'.
+
+  accum[P] is the accumulated normalized sample value for Plane P.
 
   Iff 'haveOpacity', Plane 'opacityPlane' of the tuple is an opacity
   (alpha, transparency) plane.
@@ -1322,18 +1323,15 @@ addInPixel(const struct pam * const pamP,
     unsigned int plane;
 
     for (plane = 0; plane < pamP->depth; ++plane) {
-        sample adjustedForOpacity;
+        double const normalizedSample = (double)tuple[plane]/pamP->maxval;
+        double opacityAdjustment;
         
-        if (haveOpacity && plane != opacityPlane) {
-            float const opacity = (float)tuple[opacityPlane]/pamP->maxval;
-            float const unadjusted = (float)tuple[plane]/pamP->maxval;
-
-            adjustedForOpacity = 
-                floatToSample(unadjusted * opacity, pamP->maxval);
-        } else
-            adjustedForOpacity = tuple[plane];
+        if (haveOpacity && plane != opacityPlane)
+            opacityAdjustment = (double)tuple[opacityPlane]/pamP->maxval;
+        else
+            opacityAdjustment = 1;
         
-        accum[plane] += (double)adjustedForOpacity * weight;
+        accum[plane] += opacityAdjustment * normalizedSample * weight;
     }
 }
 
@@ -1349,11 +1347,13 @@ generateOutputTuple(const struct pam * const pamP,
   Convert the values accum[] accumulated for a pixel by
   outputOneResampledRow() to a bona fide PAM tuple as *tupleP,
   as described by *pamP.
+
+  accum[P] is the pixel's plane P value normalized (i.e. in range 0..1).
 -----------------------------------------------------------------------------*/
     unsigned int plane;
 
     for (plane = 0; plane < pamP->depth; ++plane) {
-        float opacityAdjustedSample;
+        float opacityAdjustedSample;  /* normalized sample value */
 
         if (haveOpacity && plane != opacityPlane) {
             if (accum[opacityPlane] < EPSILON) {
@@ -1364,7 +1364,7 @@ generateOutputTuple(const struct pam * const pamP,
         } else
             opacityAdjustedSample = accum[plane];
 
-        (*tupleP)[plane] = floatToSample(opacityAdjustedSample, pamP->maxval);
+        (*tupleP)[plane] = unnormalize(opacityAdjustedSample, pamP->maxval);
     }
 }
 
@@ -1388,7 +1388,7 @@ outputOneResampledRow(const struct pam * const outpamP,
 
    'line' and 'accum' are just working space that Caller provides us
    with to save us the time of allocating it.  'line' is at least big
-   enough to hold an output row; 'weight' is at least outpamP->depth
+   enough to hold an output row; 'accum' is at least outpamP->depth
    big.
 -----------------------------------------------------------------------------*/
     unsigned int col;
@@ -1398,6 +1398,11 @@ outputOneResampledRow(const struct pam * const outpamP,
 
     pnm_getopacity(outpamP, &haveOpacity, &opacityPlane);
 
+    /* We accumulate intensity in accum[], where accum[P] is the intensity
+       for Plane P.  These are normalized values (i.e. in the range
+       0..1
+    */
+
     for (col = 0; col < outpamP->width; ++col) {
         WLIST const XW = XWeight[col];
 
@@ -1528,9 +1533,9 @@ resample(struct pam *     const inpamP,
     unsigned int maxRowWeights;
 
     tuple * line;
-        /* This is just work space for outputOneSampleRow() */
+        /* This is just work space for outputOneResampledRow() */
     double * weight;
-        /* This is just work space for outputOneSampleRow() */
+        /* This is just work space for outputOneResampledRow() */
 
     if (linear)
         pm_error("You cannot use the resampling scaling method on "
-- 
cgit 1.4.1