Bug #43475 [Asn->Csd]: Thick styled lines have scrambled patterns

Edit report at https://bugs.php.net/bug.php?id=43475&edit=1 ID: 43475 Updated by: cmb@php.net Reported by: lb2048 at pobox dot com Summary: Thick styled lines have scrambled patterns -Status: Assigned +Status: Closed Type: Bug Package: GD related Operating System: * PHP Version: 5.2CVS-2008-10-30 Assigned To: cmb Block user comment: N Private report: N New Comment: Automatic comment on behalf of cmb Revision: http://git.php.net/?p=php-src.git;a=commit;h=8aa511f1fc8123bba6107fa856b0b6bf298de87c Log: Fix #43475: Styled thick horizontal lines are scrambled Previous Comments: ------------------------------------------------------------------------ [2016-06-15 16:14:01] cmb@php.net The bug has been fixed in libgd, so I'm reopening. ------------------------------------------------------------------------ [2015-06-11 17:15:59] cmb@php.net The libgd ticket: <https://github.com/libgd/libgd/issues/167>. ------------------------------------------------------------------------ [2015-06-11 17:15:26] cmb@php.net I have filed a ticket against libgd now. I've noticed a minor issue wrt. to jacQues' ImageStyleThicken() function: it only works correctly for even thickness values, because libgd rounds odd thickness values to the next smaller even value. ------------------------------------------------------------------------ [2015-06-11 12:53:21] cmb@php.net Sorry for the late reply. > Horizontal thick lines patterns look scrambled to me. Indeed! I had a closer look at the issue, and found that horizontal and vertical lines do call gdImageFilledRectangle when the thickness is greater than 1 for performance reasons. The relevant code of gdImageFilledRectangle[1] loops over the x and y coordinates, and calls gdImageSetPixel which iterates over the style pattern[2]. As is, this works fine for vertical lines, but not for horizontal lines. Swapping the for loops in gdImageFilledRectangle will make horizontal lines look fine, but will break vertical lines. I'm not sure (yet) how to solve this issue, but anyhow, this is an issue that should preferably be fixed upstream in libgd. I'll file a bug report there later, and switch this ticket to "suspended" until a resolution is found. [1] <https://github.com/php/php-src/blob/PHP-5.6.9/ext/gd/libgd/gd.c#L2145-L2149> [2] <https://github.com/php/php-src/blob/PHP-5.6.9/ext/gd/libgd/gd.c#L724-L735> ------------------------------------------------------------------------ [2015-05-08 00:05:54] lb2048 at pobox dot com I agree that changing the way it works would be bad, and the way it works should be better documented. I do not agree that the issue raised by "jacQues" has been fixed. After replicating my pattern bits by the line thickness, as stated in that comment, I do see reasonable thick styled lines, except for horizontal lines. Horizontal thick lines patterns look scrambled to me. (jacQues said in 2010 that vertical lines were also bad. I don't see that now - my vertical lines seem OK.) Now using php-5.6.8; same results with php-5.5.24. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=43475 -- Edit this bug report at https://bugs.php.net/bug.php?id=43475&edit=1