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Something is wrong with ALLELM02.CGM. It includes an ESCAPE element towards the end (starting at byte 0x420) that seems to use a different format of data record (not conforming to what 8632-3 includes as NOTE 12 of Table 1 and 8632-1 in Annex H.2.2).
However, within the same package, there are other files (ESCAPE01.CGM and ESCAPE02.CGM) that include a working SDR.

ALLELM02.CGM

00000420h: 60 2F FF 9B 0C 60 45 73 63 61 70 65 44 61 74 61 ; \`/ÿ›.\`EscapeData
00000430h: 27                                              ; '

60 2F is the Command Header (Class 6, Id 1, Length 15)
FF 9B should be the ESCAPE identifier (P1)
❗ a SDR length similar to S/SF type should follow?
0C is the data type index String
❗ the data element count should follow?
60 45 73 63 61 70 65 44 61 74 61 is the encoded string "EscapeData"

ESCAPE01.CGM

0000012eh: 60 2E 00 16 0B 00 05 00 01 00 01 00 02 00 01 00 ; `...............

60 2E is the Command Header (Class 6, Id 1, Length 14)
00 16 is the ESCAPE identifier (P1) for item 22 "Transparent Cell Color"
0B is the S/SF style SDR length
00 05 is the data type index Enumerated
00 01 is the data entry count 1 (one entry)
00 01 is the encoded value 1 (one), conforming to the Escape Transparency Indicator "on"
00 02 is the data type index ColorIndex
00 01 is the data entry count 1 (one entry)
00 is the encoded value 0 (zero), conforming to the Escape Transparent Cell Color Specifier "Color Index 0"

能实现CGM图形浏览吗？