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HELIOS developer specifications
OPI image reference specification
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OPI producer (PostScript or direct PDF output) include several OPI comments to allow post processing solutions to replace content according to the comments. The "ALDImageFileName" comment is being used by HELIOS ImageServer and other vendors to reference the linked files. In remote/offside layout workflows the low-resolution files are often used with local disk path names, therefore the "ALDImageFileName" fails finding the linked content. As a second option, OPI solutions can use the "ALDImageID" comment to find the original linked file on the server. OPI producers should generate an "ALDImageID" OPI comment from the placed files.
Several producers generate the "ALDImageID" for placed TIFF files. This documentation explains how the "ALDImageID" can be found in TIFF, JPEG, and EPSF files for unmodified inclusion into the OPI comments.
How to find the data for the "ALDImageID" comment?
For TIFF files
The image reference is stored using a private TIFF tag:
| Tag number: | 34840 | |
| Tag type: | ASCII | |
| Value: | Image reference (zero terminated string) |
For EPSF files (Mac EPSF and Binary EPS)
The HELIOS image reference is stored using a private DSC comment:
| %HELRefID: | (Image reference string) |
For JPEG files
The image reference is stored in a HELIOS APP11 marker.
The HELIOS APP11 marker consists of:
- A HeliosJPEGMarker,
- One ore more HeliosJPEGResources,
- 4 zero bytes as an end marker.
The image reference is stored in the HeliosJPEGResource with type "HSID". There can be other HeliosJPEGResources in the APP11 marker which must be skipped when searching for the HELIOS Image ID.
| HeliosJPEGMarker: | ||||
| Length | Field | Comment | ||
| 2 | markerID | Always 0xFF 0xEB | ||
| 2 | markerLength | Overall length of APP11 marker as defined for the JPEG format | ||
| 7 | magic | "HELIOS" with terminating zero byte | ||
| 2 | version | Always 0x0065 (version 101) | ||
| 1 | type | Object type (can be ignored) | ||
| 1 | quality | Object quality (can be ignored) | ||
| HeliosJPEGResource: | ||||
| Length | Field | Comment | ||
| 4 | type | Resource type, for the image reference this is 0x48 0x53 0x49 0x44 ("HSID") | ||
| 4 | creator | Always 0x48 0x4f 0x50 0x49 ("HOPI") | ||
| 2 | len | Length of following data | ||
| <len> | data | Data | ||
All integers are stored in big-endian (MSB) byte order.
Sample files
Layout files containing an image reference can be downloaded from HELIOS WebShare
(UserName: tools, Password: tools). Go to "HELIOS Tools", select "OPI images with references" and click on "Download".
This will download a ZIP archive containing several layout files (TIFF, EPS, PC-EPS, and JPEG).
All layout files contain the required data for the "ALDImageID" comment as described above.
Sample OPI PostScript output
The following PostScript output should be generated by an OPI application if the
sample layout files are placed in the document: