[poppler] utils/pdftoppm.cc

[GitLab Mirror]

 utils/pdftoppm.cc |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

New commits:
commit e21c83650f15a197b286f8eed8c7d723c6900925
Author: Oliver Sander <oliver.sander at tu-dresden.de>
Date:   Wed Feb 10 21:36:51 2021 +0100

    pdftoppm: Fix rounding bug in computation of output bitmap size
    
    When a specific output image size was requested, the code would use
    that size to compute the target resolution, and then use the
    resolution to get the image size back.  In finite-precision
    arithmetic the resulting image size is not necessarily an
    integer, and a subsequent call to `ceil` then sometimes lead to
    an image size that was 1 larger than what was explicitly
    requested.
    
    Fix this by using a given image size directly, without converting
    it to resolution and back.
    
    BUG: https://gitlab.freedesktop.org/poppler/poppler/issues/927

diff --git a/utils/pdftoppm.cc b/utils/pdftoppm.cc
index 1789aadf..97fdbea2 100644
--- a/utils/pdftoppm.cc
+++ b/utils/pdftoppm.cc
@@ -628,23 +628,34 @@ int main(int argc, char *argv[])
         if (scaleDimensionBeforeRotation && needToRotate(doc->getPageRotate(pg)))
             std::swap(pg_w, pg_h);
 
+        // Handle requests for specific image size
         if (scaleTo != 0) {
             resolution = (72.0 * scaleTo) / (pg_w > pg_h ? pg_w : pg_h);
             x_resolution = y_resolution = resolution;
+            pg_w = pg_h = scaleTo;
         } else {
             if (x_scaleTo > 0) {
                 x_resolution = (72.0 * x_scaleTo) / pg_w;
+                pg_w = x_scaleTo;
                 if (y_scaleTo == -1)
                     y_resolution = x_resolution;
             }
+
             if (y_scaleTo > 0) {
                 y_resolution = (72.0 * y_scaleTo) / pg_h;
+                pg_h = y_scaleTo;
                 if (x_scaleTo == -1)
                     x_resolution = y_resolution;
             }
+
+            // No specific image size requested---compute the size from the resolution
+            if (x_scaleTo <= 0) {
+                pg_w = pg_w * (x_resolution / 72.0);
+            }
+            if (y_scaleTo <= 0) {
+                pg_h = pg_h * (y_resolution / 72.0);
+            }
         }
-        pg_w = pg_w * (x_resolution / 72.0);
-        pg_h = pg_h * (y_resolution / 72.0);
 
         if (!scaleDimensionBeforeRotation && needToRotate(doc->getPageRotate(pg)))
             std::swap(pg_w, pg_h);