projects / wxWidgets.git / blame
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1 | <HTML> |
| 2 | <HEAD> | |
| 3 | <TITLE> | |
| 4 | Introduction to the TIFF Documentation | |
| 5 | </TITLE> | |
| 6 | </HEAD> | |
| 7 | <BODY BGCOLOR=white> | |
| 8 | <FONT FACE="Arial, Helvetica, Sans"> | |
| 9 | <H1> | |
| 10 | <IMG SRC=images/strike.gif WIDTH=128 HEIGHT=100 ALIGN=left HSPACE=6> | |
| 11 | Introduction to the TIFF Documentation | |
| 12 | </H1> | |
| 13 | ||
| 14 | ||
| 15 | <P> | |
| 16 | The following definitions are used throughout this documentation. | |
| 17 | They are consistent with the terminology used in the TIFF 6.0 specification. | |
| 18 | ||
| 19 | <DL> | |
| 20 | <DT><I>Sample</I> | |
| 21 | <DD>The unit of information stored in an image; often called a | |
| 22 | channel elsewhere. Sample values are numbers, usually unsigned | |
| 23 | integers, but possibly in some other format if the SampleFormat | |
| 24 | tag is specified in a TIFF | |
| 25 | <DT><I>Pixel</I> | |
| 26 | <DD>A collection of one or more samples that go together. | |
| 27 | <DT><I>Row</I> | |
| 28 | <DD>An Nx1 rectangular collection of pixels. | |
| 29 | <DT><I>Tile</I> | |
| 30 | <DD>An NxM rectangular organization of data (or pixels). | |
| 31 | <DT><I>Strip</I> | |
| 32 | <DD>A tile whose width is the full image width. | |
| 33 | <DT><I>Compression</I> | |
| 34 | <DD>A scheme by which pixel or sample data are stored in | |
| 35 | an encoded form, specifically with the intent of reducing the | |
| 36 | storage cost. | |
| 37 | <DT><I>Codec</I> | |
| 38 | <DD>Software that implements the decoding and encoding algorithms | |
| 39 | of a compression scheme. | |
| 40 | </UL> | |
| 41 | ||
| 42 | <P> | |
| 43 | In order to better understand how TIFF works (and consequently this | |
| 44 | software) it is important to recognize the distinction between the | |
| 45 | physical organization of image data as it is stored in a TIFF and how | |
| 46 | the data is interpreted and manipulated as pixels in an image. TIFF | |
| 47 | supports a wide variety of storage and data compression schemes that | |
| 48 | can be used to optimize retrieval time and/or minimize storage space. | |
| 49 | These on-disk formats are independent of the image characteristics; it | |
| 50 | is the responsibility of the TIFF reader to process the on-disk storage | |
| 51 | into an in-memory format suitable for an application. Furthermore, it | |
| 52 | is the responsibility of the application to properly interpret the | |
| 53 | visual characteristics of the image data. TIFF defines a framework for | |
| 54 | specifying the on-disk storage format and image characteristics with | |
| 55 | few restrictions. This permits significant complexity that can be | |
| 56 | daunting. Good applications that handle TIFF work by handling as wide | |
| 57 | a range of storage formats as possible, while constraining the | |
| 58 | acceptable image characteristics to those that make sense for the | |
| 59 | application. | |
| 60 | ||
| 61 | ||
| 62 | <P> | |
| 63 | <HR> | |
| 64 | ||
| 65 | Last updated: $Date: 1999/08/09 20:21:21 $ | |
| 66 | ||
| 67 | </BODY> | |
| 68 | </HTML> |