imagemagick parameters for avoiding tIME chunk incorrect

[BenLubar]

Steps to reproduce the problem

1. Upload an image.

Expected behaviour

There should not be a modification time encoded into the file.

Actual behaviour

There is a modification time encoded into the file.

Detailed description

Mastodon instance

No response

Mastodon version

No response

Technical details

This should be a simple find-and-replace to fix.

[unascribed]

+set date:timestamp is also needed to remove the final timestamp tEXt chunk. These strings match the keywords used in the tEXt chunks, so this looks like a transcription mistake, but there's no harm in keeping the "broken" ones too in case they do work on older versions of ImageMagick — or other file formats such as JPEG or WebP.

This is (and has been, for an unknown length of time) breaking PNG dedupe on Jortage; my thread on this is what called Ben Lubar's attention to it and resulted in them opening the issue.

Hexdump of a bad PNG file created by Mastodon

00000000  89 50 4e 47 0d 0a 1a 0a  00 00 00 0d 49 48 44 52  |.PNG........IHDR|
00000010  00 00 00 01 00 00 00 01  01 00 00 00 00 37 6e f9  |.............7n.|
00000020  24 00 00 00 04 67 41 4d  41 00 00 b1 8f 0b fc 61  |$....gAMA......a|
00000030  05 00 00 00 20 63 48 52  4d 00 00 7a 26 00 00 80  |.... cHRM..z&...|
00000040  84 00 00 fa 00 00 00 80  e8 00 00 75 30 00 00 ea  |...........u0...|
00000050  60 00 00 3a 98 00 00 17  70 9c ba 51 3c 00 00 00  |`..:....p..Q<...|
00000060  02 62 4b 47 44 00 01 dd  8a 13 a4 00 00 00 07 74  |.bKGD..........t|
00000070  49 4d 45 07 e7 09 18 13  0b 1b 28 d9 91 95 00 00  |IME.......(.....|
00000080  00 0a 49 44 41 54 08 d7  63 68 00 00 00 82 00 81  |..IDAT..ch......|
00000090  dd 43 6a f4 00 00 00 25  74 45 58 74 64 61 74 65  |.Cj....%tEXtdate|
000000a0  3a 63 72 65 61 74 65 00  32 30 32 33 2d 30 39 2d  |:create.2023-09-|
000000b0  32 34 54 31 39 3a 31 31  3a 32 37 2b 30 30 3a 30  |24T19:11:27+00:0|
000000c0  30 58 fe ec bc 00 00 00  25 74 45 58 74 64 61 74  |0X......%tEXtdat|
000000d0  65 3a 6d 6f 64 69 66 79  00 32 30 32 33 2d 30 39  |e:modify.2023-09|
000000e0  2d 32 34 54 31 39 3a 31  31 3a 32 37 2b 30 30 3a  |-24T19:11:27+00:|
000000f0  30 30 29 a3 54 00 00 00  00 28 74 45 58 74 64 61  |00).T....(tEXtda|
00000100  74 65 3a 74 69 6d 65 73  74 61 6d 70 00 32 30 32  |te:timestamp.202|
00000110  33 2d 30 39 2d 32 34 54  31 39 3a 31 31 3a 31 31  |3-09-24T19:11:11|
00000120  2b 30 30 3a 30 30 93 e9  47 06 00 00 00 00 49 45  |+00:00..G.....IE|
00000130  4e 44 ae 42 60 82                                 |ND.B`.|
00000136

Hexdump of a file created with the OP's "fixed" command

00000000  89 50 4e 47 0d 0a 1a 0a  00 00 00 0d 49 48 44 52  |.PNG........IHDR|
00000010  00 00 00 01 00 00 00 01  01 00 00 00 00 37 6e f9  |.............7n.|
00000020  24 00 00 00 20 63 48 52  4d 00 00 7a 26 00 00 80  |$... cHRM..z&...|
00000030  84 00 00 fa 00 00 00 80  e8 00 00 75 30 00 00 ea  |...........u0...|
00000040  60 00 00 3a 98 00 00 17  70 9c ba 51 3c 00 00 00  |`..:....p..Q<...|
00000050  02 62 4b 47 44 00 01 dd  8a 13 a4 00 00 00 0a 49  |.bKGD..........I|
00000060  44 41 54 08 d7 63 68 00  00 00 82 00 81 dd 43 6a  |DAT..ch.......Cj|
00000070  f4 00 00 00 28 74 45 58  74 64 61 74 65 3a 74 69  |....(tEXtdate:ti|
00000080  6d 65 73 74 61 6d 70 00  32 30 32 33 2d 30 39 2d  |mestamp.2023-09-|
00000090  32 34 54 31 39 3a 31 32  3a 34 35 2b 30 30 3a 30  |24T19:12:45+00:0|
000000a0  30 c4 71 d6 72 00 00 00  00 49 45 4e 44 ae 42 60  |0.q.r....IEND.B`|
000000b0  82                                                |.|
000000b1

Note that while the tIME chunk is indeed now gone, there is still a tEXt chunk of type date:timestamp containing the same data. Adding +set date:timestamp creates a file that is truly lacking all time information.

Hexdump of a file created via convert xc: +profile '!icc,*' +set date:modify +set date:create +set date:timestamp test.png

00000000  89 50 4e 47 0d 0a 1a 0a  00 00 00 0d 49 48 44 52  |.PNG........IHDR|
00000010  00 00 00 01 00 00 00 01  01 00 00 00 00 37 6e f9  |.............7n.|
00000020  24 00 00 00 20 63 48 52  4d 00 00 7a 26 00 00 80  |$... cHRM..z&...|
00000030  84 00 00 fa 00 00 00 80  e8 00 00 75 30 00 00 ea  |...........u0...|
00000040  60 00 00 3a 98 00 00 17  70 9c ba 51 3c 00 00 00  |`..:....p..Q<...|
00000050  02 62 4b 47 44 00 01 dd  8a 13 a4 00 00 00 0a 49  |.bKGD..........I|
00000060  44 41 54 08 d7 63 68 00  00 00 82 00 81 dd 43 6a  |DAT..ch.......Cj|
00000070  f4 00 00 00 00 49 45 4e  44 ae 42 60 82           |.....IEND.B`.|
0000007d

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I'm adding a workaround for this to poolmgr, but it would be nice to see this fixed in upstream — these timestamps are unnecessary metadata.