Graphics Importers
QPix accomplishes most of its functionality with the help of QuickTime's graphics import components, aka "graphics importers".
High-level QPix commands dealing with image files and plug-in areas use graphics importers internally, but hide potentially confusing details. However, in order to provide the most of QuickTime's capabilities and flexibility, QPix also includes a set of low-level commands for directly working with graphics importers.
Graphics importers are code modules. Each importer "knows" all the details of a specific graphic file format and provides specific services to the client software. Graphics importers have the following properties:
Type (String4) (In pure IM terms, this is the component subtype field)
Flags (Longint)
Name (String255)
The files supported by a graphics importer are specified by the importer's type in conjunction with bit #12 of the flags property. If bit #12 is off, the importer's type is the Mac file type of the supported files. If bit #12 is on, it is a filename extension.
Examples
- Type: '8BPS'
- Flags: 0x40000000
- Name: Photoshop
This is the Photoshop importer. It supports files of type '8BPS' (0x40000000 bit #12 is false).
- Type: 'GIF '
- Flags: 0x40001200
- Name: GIF
This importer knows how to handle GIF files. It supports files with the .GIF filename extension (0x40001200 bit #12 is true).
Notes
1. Some terms and concepts are paraphrased in this chapter in an attempt to better match 4D's terminology and way of doing things. For reference material, check QuickTime Developer's Documentation.
2. When working with graphics importers, you will need to create an importer instance, work with it, and destroy it when no longer needed.
Commands
| QPx_NewImporterForFile | Create a graphics importer instance for the image stored in a file |
| QPx_NewImporterForData | Create a graphics importer instance for the image data stored in a BLOB |
| QPx_NewImporterForURL | Create a graphics importer from a URL |
| QPx_NewImporterForPict | Create a graphics importer instance for the image data in a picture variable |
| QPx_NewImporter | Create a graphics importer instance without image data |
| QPx_FreeImporter | Destroy an existing importer instance |
| QPx_SetImporterFile | Assign an image file to a graphics importer |
| QPx_GetImporterFile | Get the path of the file associated with a graphics importer |
| QPx_SetImporterData | Assign image data from a BLOB to a graphics importer |
| QPx_GetImporterData | Get the image data associated with a graphics importer |
| QPx_SetImporterOffsetAndLimit | Specify start and end of data within the image source |
| QPx_GetImporterOffsetAndLimit | Get the start and end of data within the image source container |
| QPx_ValidateImporter | Ask importer to test its image data |
| QPx_GetImporterImageSize | Get the dimensions of the image associated with an importer |
| QPx_GetImporterImageRes | Get the resolution of the image associated with an importer |
| QPx_GetImporterImageDepth | Get the pixel depth of the image associated with an importer |
| QPx_GetImporterInfo | Get information about an importer |
| QPx_GetImporterColorSpace | Get the color space of the image associated with an importer |
| QPx_GetImporterColorProfile | Get the color profile of the image associated with an importer |
| QPx_GetImporterEmbeddedThumb | Get the embedded thumbnail from an image |
| QPx_CreateImporterThumbnail | Create high-quality thumbnail from image data associated with an importer |
| QPx_ReadImporterImageInPict | Read the image associated with an importer into a 4D picture variable |
| QPx_ExportImporterImage | Export the image associated with an importer to file in a specified format |
| QPx_ExportImporterImageToBLOB | Export the image associated with an importer to a BLOB in a specified format |
| QPx_GetImporterTagContainer | Extract the tag container from the image associated with an importer |
| QPx_CountImporterFrames | Get the number of frames of a multi-frame image |
| QPx_SetImporterFrameIndex | Set the current frame in a multi-frame image |
| QPx_GetImporterFrameIndex | Get the current frame of a multi-image image |
| QPx_GetImporterFrameType | Get the type of a frame in a multi-frame image |