warn and ignore too-small image resolutions; from Max Chernoff

git-svn-id: svn://tug.org/texlive/trunk/Build/source@73494 c570f23f-e606-0410-a88d-b1316a301751

texk/web2c/pdftexdir/ChangeLog

@@ -1,3 +1,10 @@
+2025-01-17  Max Chernoff  <[email protected]>
+
+	* pdftex.web (Glob..., Set init...): new global
+	resolution_ratio==226.
+	(scale_image): use it to report a warning for too-small resolutions
+	(e.g., 1px x 1px). https://tex.stackexchange.com/questions/734919
+
 2024-08-04  Thanh Han The  <[email protected]>
 
 	* pdftoepdf.cc (write_epdf): reversed sep and pdfkeyprefix.

texk/web2c/pdftexdir/NEWS

@@ -4,6 +4,8 @@
     entries use an _ instead of ., as in PTEX_Fullbanner.
 - bugfixes:
   - increase tolerance for detecting interword spaces in overfull lines.
+  - ignore tiny resolutions like 1x1 embedded in images instead of
+    exceeding \maxdimen.
 
 pdfTeX 3.141592653-2.6-1.40.26 (TeX Live 2024)
 - bugfixes:

texk/web2c/pdftexdir/pdftex.web

@@ -15787,6 +15787,7 @@ accuracy.
 @!ten_pow: array[0..9] of integer; {$10^0..10^9$}
 @!scaled_out: integer; {amount of |scaled| that was taken out in
 |divide_scaled|}
+@!resolution_ratio: integer; {(1in in sp)/|\maxdimen|}
 @!init_pdf_output: boolean;
 @!adv_char_width_s: integer; {to save result of calculation done in |adv_char_width| }
 @!adv_char_width_s_out: scaled;
@@ -15795,6 +15796,7 @@ accuracy.
 one_bp := 65782; {65781.76}
 one_hundred_bp := 6578176;
 one_hundred_inch := 473628672;
+resolution_ratio := 226;
 ten_pow[0] := 1;
 for i := 1 to 9 do
     ten_pow[i] := 10*ten_pow[i - 1];
@@ -34429,6 +34431,13 @@ begin
     end;
     if (x <= 0) or (y <= 0) or (xr < 0) or (yr < 0) then
         pdf_error("ext1", "invalid image dimensions");
+    if (x / resolution_ratio >= xr) or (y / resolution_ratio >= yr) then begin
+        {It's better to warn and ignore too-small resolutions given in
+         the image file, usually 1dpi x 1dpi, to avoid arithmetic overflow.}
+        xr := 0;
+        yr := 0;
+        pdf_warning("ext1", "too small image resolution ignored", true, true);
+    end;
     if is_pdf_image(image) then begin
         w := x;
         h := y;