resolves #1048 flaw in generating gradient pattern key

[jacksop]

Packing gradient attributes down to 8-bit values causes collisions when generating the SHA1 digest.

Concatinate the gradient attributes into a string in order to calculate the digest for the key.

[jacksop]

Had an issue with the manual spec. Not sure why the hash has changed 🤔

[pointlessone]

I think, gradient IDs changed with this PR. So the manual has changed as well. Make sure those are the only changes.

[jacksop]

Produced the manual in both Ruby and JRuby to confirm no unexpected changes. The following is a diff from the Ruby produced pdf.

--- a/new_man.pdf
+++ b/old_man.pdf
@@ -28295,37 +28295,37 @@ S
 [] 0 d
 10 w
 /Pattern cs
-/SPb2ac70e4092a30e61b731f0ddcce5d2504387e26 scn
+/SPc027eb13458c6a3a5e5bb248c66f0a9bda7e3ae5 scn
 36.0 186.0 100.0 100.0 re
 f
 /Pattern CS
-/SP9bc3d87486885cdd70bcc232bdb8390eb40b3406 SCN
+/SP143b3ff7c833028e87374381ce150c291c83c0a5 SCN
 186.0 186.0 100.0 100.0 re
 S
-/SP88db9f7dce277b8129cdf156cddfc04f1f03f97e scn
-/SPfe1deee7ddb28305363bf0b8499100bb5c6398dc SCN
+/SP1ff2cc60c143e283d45a23e66ec1471a5b7d85cf scn
+/SP4c162120d6599fd9f1e63b83fad681f42ff7e303 SCN
 336.0 186.0 100.0 100.0 re
 b
 q
 1.00000 0.00000 0.00000 1.00000 323.86797 -309.88644 cm
 q
 0.70711 0.70711 -0.70711 0.70711 0.00000 0.00000 cm
-/SPc0f96e6212ed723e20c7902080036d459b015f36 scn
+/SP6f68d2e29b15a5532c23070e22d7bd7c06bc52ee scn
 496.0 196.0 80.0 80.0 re
 f
 Q
 Q
-/SPc45c6ba25edd986cedc8481d02073dc33a93cf0b scn
+/SP8256b94b16aea0a7d1641d75dd5d8e296895f9ae scn
 36.0 36.0 100.0 100.0 re
 f
-/SPeac6fb4ee24b0a4a6337258aaeadc4b81ee57327 SCN
+/SP47d5de4ca76cc74d261d227e82a96e3f6111ff74 SCN
 186.0 36.0 100.0 100.0 re
 S
-/SPfbad10aa6625193155391a3905abf363078813bc SCN
-/SP2e5547f809c03cb6a532e7f1d432ffe3ac3d39f6 scn
+/SP7825f5024162679626a2bc82fa41f9c8145d9c1a SCN
+/SPd26d3d41fe66bcec38ce4b605d8267af56155a59 scn
 336.0 36.0 100.0 100.0 re
 b
-/SP02b2d2a7b384f69b8f0bff4a895a70c84e8b2bd5 scn
+/SPf13c6a82cfdc4418087e761196d8fb506ae16f5d scn
 486.0 36.0 100.0 100.0 re
 f
 1 w
@@ -28354,16 +28354,16 @@ endobj
 /F1.0 17 0 R
 /F3.0 11 0 R
 >>
-/Pattern << /SPb2ac70e4092a30e61b731f0ddcce5d2504387e26 97 0 R
-/SP9bc3d87486885cdd70bcc232bdb8390eb40b3406 100 0 R
-/SP88db9f7dce277b8129cdf156cddfc04f1f03f97e 103 0 R
-/SPfe1deee7ddb28305363bf0b8499100bb5c6398dc 106 0 R
-/SPc0f96e6212ed723e20c7902080036d459b015f36 112 0 R
-/SPc45c6ba25edd986cedc8481d02073dc33a93cf0b 115 0 R
-/SPeac6fb4ee24b0a4a6337258aaeadc4b81ee57327 118 0 R
-/SPfbad10aa6625193155391a3905abf363078813bc 121 0 R
-/SP2e5547f809c03cb6a532e7f1d432ffe3ac3d39f6 124 0 R
-/SP02b2d2a7b384f69b8f0bff4a895a70c84e8b2bd5 127 0 R
+/Pattern << /SPc027eb13458c6a3a5e5bb248c66f0a9bda7e3ae5 97 0 R
+/SP143b3ff7c833028e87374381ce150c291c83c0a5 100 0 R
+/SP1ff2cc60c143e283d45a23e66ec1471a5b7d85cf 103 0 R
+/SP4c162120d6599fd9f1e63b83fad681f42ff7e303 106 0 R
+/SP6f68d2e29b15a5532c23070e22d7bd7c06bc52ee 112 0 R
+/SP8256b94b16aea0a7d1641d75dd5d8e296895f9ae 115 0 R
+/SP47d5de4ca76cc74d261d227e82a96e3f6111ff74 118 0 R
+/SP7825f5024162679626a2bc82fa41f9c8145d9c1a 121 0 R
+/SPd26d3d41fe66bcec38ce4b605d8267af56155a59 124 0 R
+/SPf13c6a82cfdc4418087e761196d8fb506ae16f5d 127 0 R
 >>
 >>
 >>

[pointlessone]

All changes to the manual seem to be expected.

[pointlessone]

Could you please add spec that checks for collision that used to be generated?