Difference between revisions of "Working with Multimedia Data"
Yvonnemilne (Talk | contribs) |
Yvonnemilne (Talk | contribs) |
||
| (15 intermediate revisions by one user not shown) | |||
| Line 1: | Line 1: | ||
==Working with Multimedia Data== | ==Working with Multimedia Data== | ||
| − | + | Multimedia data can be stored in Recital tables in object [[Appendix A|datatype]] fields. The data is stored in binary large object (BLOB) format in the ''.dbt'' file, with a corresponding pointer in the table record. | |
| − | + | ||
| − | + | Recital provides the following functions to handle the transfer and querying of multimedia data: | |
| − | + | * [[OBJECTREAD()|objectread()]] - read a binary file into a Recital object field | |
| + | * [[OBJECTWRITE()|objectwrite()]] - write the contents of a Recital object field to a binary file | ||
| + | * [[OBJECTTYPE()|objecttype()]] - return the type of a Recital object field, e.g. ''jpg'' | ||
| − | + | ===Inserting Multimedia Data=== | |
| + | <pre> | ||
| + | objectread(<filename as character>,<fieldname as character>) | ||
| + | </pre> | ||
| − | + | The [[OBJECTREAD()|objectread()]] function reads an external binary file into a Recital object field. It returns true (.T.) if the operation was successful, and false (.F.) otherwise. | |
| − | + | ||
| − | + | ||
| − | The | + | The file to read in is specified in <filename>, and can be any valid Recital expression that returns a valid file name. The first three characters of the file extension are stored in the object field as the object's type, as returned by the [[OBJECTTYPE()|objecttype()]] function. |
| − | The name of the file to create can be specified in the parameter <filename>. This can be any valid Recital | + | The field into which the file is placed is specified in <object field>, and must be a Recital object field in the currently selected workarea. |
| + | |||
| + | '''Example''' | ||
| + | |||
| + | <code lang="recital"> | ||
| + | open database southwind | ||
| + | use categories | ||
| + | objectread("newpic.jpg",picture) | ||
| + | close databases | ||
| + | </code> | ||
| + | |||
| + | ===Retrieving Multimedia Data=== | ||
| + | |||
| + | <pre> | ||
| + | objectwrite(<filename as character>,<fieldname as character> [, <tempfile as logical>]) | ||
| + | </pre> | ||
| + | |||
| + | The [[OBJECTWRITE()|objectwrite()]] function writes an external binary file from a Recital object field. The objectwrite() function returns true (.T.) if the external binary file was created successfully, and false (.F.) otherwise. | ||
| + | |||
| + | The name of the file to create can be specified in the parameter <filename>. This can be any valid Recital expression that returns a valid filename. The filename can also be an empty string, providing that the logical expression <expL> is true (.T.). In this case, a unique temporary file name will be generated and the object written to this file, with the file name being returned from objectwrite(). | ||
The Recital object field containing the data to be written, is specified in the parameter <object field>, and must be a valid field in the currently selected workarea. | The Recital object field containing the data to be written, is specified in the parameter <object field>, and must be a valid field in the currently selected workarea. | ||
| + | |||
| + | '''Example''' | ||
<code lang="html"> | <code lang="html"> | ||
| Line 24: | Line 47: | ||
use categories | use categories | ||
scan | scan | ||
| − | + | m_file = "__"+ltrim(str(recno()))+".jpg" | |
| − | + | ||
? '<img src="'+objectwrite(m_file,picture,.t.)+'"><br>' | ? '<img src="'+objectwrite(m_file,picture,.t.)+'"><br>' | ||
endscan | endscan | ||
| Line 33: | Line 55: | ||
</body> | </body> | ||
</code> | </code> | ||
| − | |||
| − | |||
| − | |||
Latest revision as of 16:42, 17 March 2010
Working with Multimedia Data
Multimedia data can be stored in Recital tables in object datatype fields. The data is stored in binary large object (BLOB) format in the .dbt file, with a corresponding pointer in the table record.
Recital provides the following functions to handle the transfer and querying of multimedia data:
- objectread() - read a binary file into a Recital object field
- objectwrite() - write the contents of a Recital object field to a binary file
- objecttype() - return the type of a Recital object field, e.g. jpg
Inserting Multimedia Data
objectread(<filename as character>,<fieldname as character>)
The objectread() function reads an external binary file into a Recital object field. It returns true (.T.) if the operation was successful, and false (.F.) otherwise.
The file to read in is specified in <filename>, and can be any valid Recital expression that returns a valid file name. The first three characters of the file extension are stored in the object field as the object's type, as returned by the objecttype() function.
The field into which the file is placed is specified in <object field>, and must be a Recital object field in the currently selected workarea.
Example
open database southwind use categories objectread("newpic.jpg",picture) close databases
Retrieving Multimedia Data
objectwrite(<filename as character>,<fieldname as character> [, <tempfile as logical>])
The objectwrite() function writes an external binary file from a Recital object field. The objectwrite() function returns true (.T.) if the external binary file was created successfully, and false (.F.) otherwise.
The name of the file to create can be specified in the parameter <filename>. This can be any valid Recital expression that returns a valid filename. The filename can also be an empty string, providing that the logical expression <expL> is true (.T.). In this case, a unique temporary file name will be generated and the object written to this file, with the file name being returned from objectwrite().
The Recital object field containing the data to be written, is specified in the parameter <object field>, and must be a valid field in the currently selected workarea.
Example
