ImageGear .NET
PSD
| Full Name | PSD (Adobe Photoshop) |
| Format ID | ImGearFormats.PSD |
| File Extension(s) | *.psd |
| Data Type | Raster Image |
| Data Encoding | Binary |
| Multi-Page Support | No |
| Alpha Channel Support | Supports pre-multiplied Alpha and additional Alpha mask channels as ImageGear Extra channels. |
| Metadata Update Support | Page |
| ImageGear Platforms Support | WIN32, WIN64, Unix, .NET, .NET64, .NET Compact Framework |
| Filter Control Parameter | Type | Default Value | Available Values | Description |
| LoadFirstExtraChannelAsAlpha | bool | false | false, true | This parameter specifies how ImageGear should load the first extra channel of a PSD image. If false , ImageGear loads all extra channels according to their descriptors in the file header. If the channel contains transparency information, ImageGear loads it as Alpha channel. Otherwise IG loads it as Extra channel. If true, IG loads first extra channel as Alpha channel. This mode provides backward compatibility with previous versions of ImageGear. |
| ReadLayerIndex | int | -1 | Any integer, but no more than number of layers | When > -1 specifies a zero based index of layer mask image to load, otherwise reads the composition image. |
Adobe PSD file format has different non-image data that can be stored before and after an image data. The Adobe PSD metadata design allows reading and writing the following non-image data (exactly like in System.Windows.Media.Imaging.BitmapMetadata; strings by default):
| Tag Name | Tag ID | Description |
| Signature | ImGearPSDTagIDs.SIGNATURE | Adobe Photoshop Signature: always equal to '8BPS'. |
| Version | ImGearPSDTagIDs.VERSION | Version: always equal to 1. |
| Rows | ImGearPSDTagIDs.ROWS | The height of the image in pixels. Supported range is 1 to 30,000. |
| Cols | ImGearPSDTagIDs.COLS | The width of the image in pixels. Supported range is 1 to 30,000. |
| Depth | ImGearPSDTagIDs.DEPTH | Depth: the number of bits per channel. Supported values are 1, 8, and 16. |
| ColorMode | ImGearPSDTagIDs.MODE | The color mode of the file. Supported values are: Bitmap = 0; Grayscale = 1; Indexed = 2; RGB = 3; CMYK = 4; Multichannel = 7; Duotone = 8; Lab = 9. |
| ColorModeLength | ImGearPSDTagIDs.MODE_LEN | The length of the following color data provided by tag ColorData. |
| ColorData | ImGearPSDTagIDs.COLOR_DATA | The color data. |
| PhotoshopResources | ImGearPSDTagIDs.PHOTOSHOP_RESOURCES | Photoshop Image Resource metadata group. Image resources are used to store non-pixel data associated with images. |
| Layers | ImGearPSDTagIDs.LAYERS | Photoshop Image Layer Info metadata group. Represents high-level organization of the layers information. |
| LayerCount | ImGearPSDTagIDs.LAYER_COUNT | Number of layers in the Photoshop Image. |
| Header | ImGearPSDTagIDs.HEADER | This section contains the basic properties of the image. |
| RESERVED_HDR | ImGearPSDTagIDs.RESERVED_HDR | Reserved: must be zero. |
| Channels | ImGearPSDTagIDs.CHANNELS | The number of channels in the image, including any alpha channels. Supported range is 1 to 56. |
| IPTC_NAA | ImGearPSDTagIDs.IPTC_NAA | File information (IPTC-NAA record 2). |
The PSD file is considered by many in the computer graphics arts community as an industry standard.
The PSD is organized into 5 major segments of data: the header, 3 informational blocks, and the bitmap data. The short header always contains a "signature" of 8PPS, as well as these fields: width, height, and bit depth of the bitmap.
The first block of informational data is called the "Color Mode Data Block". It begins with a value for the length of the block. If the image has a palette, it is located here.
The next block is called the "Image Resources Block". Like the previous block, it first gives the length of the block. An ID field is filled with one of many possible values that indicate the structure where the data is stored. It may contain such parameters as resolution.
The last informational block is called the "Layer and Mask Instruction Block". After a value for the length of the block, it tells how many "layer records" follow. There is a record for each layer in the image. Each record begins with a channel ID and the length of the data in the record. After the records, a "Layer Mask" section may be stored, if applicable.
The bitmap data represents the last segment of a PSD file.
Murray, James D. and William vanRyper. Encyclopedia of Graphics File Formats, 2d ed. Sebastopol, CA: OaReilly & Associates, Inc., 1996.