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fixed potential access violation in DrawPartialTrans #2

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fixed potential access violation in DrawPartialTrans #2

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20 changes: 17 additions & 3 deletions PNGImage.pas
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
{Portable Network Graphics Delphi 1.564 (31 July 2006) }
{Portable Network Graphics Delphi 1.565 (7 November 2023) }

{This is a full, open sourced implementation of png in Delphi }
{It has native support for most of png features including the }
Expand All @@ -9,6 +9,11 @@


{
Versino 1.565
2023-11-07 BUG 1 - There was a possible access violation
when applying the alpha mask because an extra
byte was read that possible fell beyond the
end of the row of pixels
Version 1.564
2006-07-25 BUG 1 - There was one GDI Palette object leak
when assigning from other PNG (fixed)
Expand Down Expand Up @@ -211,7 +216,7 @@ interface
zlibpas, pnglang;

const
LibraryVersion = '1.564';
LibraryVersion = '1.565';

{$IFNDEF UseDelphi}
const
Expand Down Expand Up @@ -4810,7 +4815,16 @@ procedure TPngObject.DrawPartialTrans(DC: HDC; Rect: TRect);
{Optmize when we don�t have transparency}
if (AlphaSource[i2] <> 0) then
if (AlphaSource[i2] = 255) then
ImageData[i] := pRGBQuad(@ImageSource[i2 * 3])^
begin
//20231107 Stijn Sanders
//ImageData[i] := pRGBQuad(@ImageSource[i2 * 3])^
//copied 4 bytes, but the 4th byte possibly falls outside of
//ImageSource on the last pixel, which may cause an access violation
ImageData[i].rgbRed := pRGBQuad(@ImageSource[i2 * 3]).rgbRed;
ImageData[i].rgbGreen := pRGBQuad(@ImageSource[i2 * 3]).rgbGreen;
ImageData[i].rgbBlue := pRGBQuad(@ImageSource[i2 * 3]).rgbBlue;
ImageData[i].rgbReserved := 0;
end
else
with ImageData[i] do
begin
Expand Down