Editing PVR

[[Category:Software]]<noinclude>[[Category:Main]]</noinclude>

<div style="float:right">[[File:Texture-Icon-AA.JPG|100px|thumb|left|Standard model image widely used]]</div>

<div style="color: #ffffff; background-color: #505652; border: 1px solid #808000; padding: 5px; {{box-shadow|4px|4px|8px|#b0b090}}">
'''P'''ower'''VR''' '''T'''exture '''C'''ompression files: PVRTC and PVRTC2 are a family of lossy, fixed-rate texture compression formats. 
</div>

PowerVR is a division of Imagination Technologies (formerly VideoLogic) that develops hardware and software for 2D and 3D rendering, and more.

== Features ==

<div style="float:right">[[File:03_PVRTC_ATITC_ETC1_BC1_comparison.png|200px|left]]</div>

*PVRTC supports both opaque (RGB) and translucent (RGBA) textures (unlike other formats such as S3TC that require a dedicated, larger form to support full alpha channels).
*competitive compression ratios.

== File format ==

The PVR (.pvr) format (specification version 3.0.0) consists of:

{| class="wikitable" style="text-align: center;"
|-
| style="background-color:#505652; color:#FFFFFF;" |'''Header'''<br />52 bytes (0x34)
| style="background-color:#505652; color:#FFFFFF;" |'''Meta Data (optional)'''<br />variable
| style="background-color:#505652; color:#FFFFFF;" |'''Texture Data'''<br />variable
|-
|}

=== Header ===

{| class="wikitable" style="text-align: center;"
|-
| style="background-color:#505652; color:#FFFFFF;" |'''Offset (h)'''
| style="background-color:#505652; color:#FFFFFF;" |'''Size (h)'''
| style="background-color:#505652; color:#FFFFFF;" |'''Example (h)'''
| style="background-color:#505652; color:#FFFFFF;" |'''Value (conversion)''' 
| style="background-color:#505652; color:#FFFFFF;" |'''Notes'''
|-
|colspan="5" style="text-align:center; background-color:lightblue;" | <span style="color:black;">PVR header</span>
|-
| 0x00 || 0x04 || 50 56 52 03 || "PVR " || '''Version:''' Contains the version of the PVR header format.
|-
| 0x04 || 0x04 || 00 00 00 00 ||  || '''Flags:'''
*00: No flag has been set
*02: Colour values within the texture have been pre-multiplied by the alpha values. 
|-
| 0x08 || 0x08 || 72 67 62 61 08 08 08 08 || "rgba" || '''Pixel Format:''' rgba + bit rate per channel
|-
| 0x10 || 0x04 || 00 00 00 00 ||  || '''Colour Space:'''
*0: Texture data is in the Linear RGB colour space
*1: Texture data is in the Standard RGB colour space 
|-
| 0x14 || 0x04 || 00 00 00 00 || 0 || '''Channel Type:'''
|-
| 0x18 || 0x04 || 00 01 00 00 || 256 || '''Height:''' width of the texture stored in the texture data, in pixels. 
|-
| 0x1C || 0x04 || 00 01 00 00 || 256 || '''Width:''' width of the texture stored in the texture data, in pixels. 
|-
| 0x20 || 0x04 || 01 00 00 00 || 1 || '''Depth:''' depth of the texture stored in the texture data, in pixels.
|-
| 0x24 || 0x04 || 01 00 00 00 || 1 || '''Num. Surfaces:''' number of surfaces within the texture array.
|-
| 0x28 || 0x04 || 01 00 00 00 || 1 || '''Num. Faces:''' number of faces in a cube map. 
|-
| 0x2C || 0x04 || 01 00 00 00 || 1 || '''MIP-Map Count:''' number of MIP-Map levels present including the top level. 
<small>
A value of one, therefore, means that only the top level texture exists.
</small>
|-
| 0x30 || 0x04 || 00 00 00 00 || 0 || '''Meta Data Size:''' allows for the creator of a PVR to store custom information within the PVR file relating to the storage. 
|-
|}

==== Pixel Format ====
If the most significant 4 bytes contain a value, the full 8 bytes are used to determine the pixel format. <br />
The least significant 4 bytes contain the channel order, each byte containing a single character, or a null character if there are fewer than four channels, e.g., {‘r’, ‘g’, ‘b’, ‘a’} or {‘r’, ‘g’, ‘b’, ‘\0’}. <br />
The most significant 4 bytes state the bit rate for each channel in the same order, each byte containing a single 8bit unsigned integer value, or zero if there are fewer than four channels, e.g., {8, 8, 8, 8} or {5, 6, 5, 0}. 


Where the most significant 4 bytes have been set to ‘0’ and the least significant 4 bytes will contain a 32bit unsigned integer value identifying the pixel format


{| class="wikitable" style="text-align: center;"
|-
| style="background-color:#505652; color:#FFFFFF;" |'''Formats'''
| style="background-color:#505652; color:#FFFFFF;" |'''Value'''
|-
|colspan="5" style="text-align:center; background-color:lightblue;" | <span style="color:black;">Identifier</span>
|-
|PVRTC 2bpp RGB || 0 
|-
|PVRTC 2bpp RGBA || 1 
|-
|PVRTC 4bpp RGB || 2 
|-
|PVRTC 4bpp RGBA || 3 
|-
|PVRTC-II 2bpp || 4 
|-
|PVRTC-II 4bpp || 5 
|-
|ETC1 || 6 
|-
|DXT1 || 7 
|-
|DXT2 || 8 
|-
|DXT3 || 9 
|-
|DXT4 || 10 
|-
|DXT5 || 11 
|-
|BC1 || 7 
|-
|BC2 || 9 
|-
|BC3 || 11 
|-
|BC4 || 12 
|-
|BC5 || 13 
|-
|BC6 || 14 
|-
|BC7 || 15 
|-
|UYVY || 16 
|-
|YUY2 || 17 
|-
|BW1bpp || 18 
|-
|R9G9B9E5 Shared Exponent || 19 
|-
|RGBG8888 || 20 
|-
|GRGB8888 || 21 
|-
|ETC2 RGB || 22 
|-
|ETC2 RGBA || 23 
|-
|ETC2 RGB A1 || 24 
|-
|EAC R11  || 25 
|-
|EAC RG11  || 26 
|-
|ASTC_4x4 || 27 
|-
|ASTC_5x4 || 28 
|-
|ASTC_5x5 || 29 
|-
|ASTC_6x5 || 30 
|-
|ASTC_6x6 || 31 
|-
|ASTC_8x5 || 32 
|-
|ASTC_8x6 || 33 
|-
|ASTC_8x8 || 34 
|-
|ASTC_10x5 || 35 
|-
|ASTC_10x6 || 36 
|-
|ASTC_10x8 || 37 
|-
|ASTC_10x10 || 38 
|-
|ASTC_12x10 || 39 
|-
|ASTC_12x12 || 40 
|-
|ASTC_3x3x3 || 41 
|-
|ASTC_4x3x3 || 42 
|-
|ASTC_4x4x3 || 43 
|-
|ASTC_4x4x4 || 44 
|-
|ASTC_5x4x4 || 45 
|-
|ASTC_5x5x4 || 46 
|-
|ASTC_5x5x5 || 47 
|-
|ASTC_6x5x5 || 48 
|-
|ASTC_6x6x5 || 49 
|-
|ASTC_6x6x6 || 50  
|-
|}

==== Channel Type ====
the data type of the colour channels within the texture data. 

{| class="wikitable" style="text-align: center;"
|-
| style="background-color:#505652; color:#FFFFFF;" |'''Data Type'''
| style="background-color:#505652; color:#FFFFFF;" |'''Value'''
|-
|Unsigned Byte Normalised || 0 
|-
|Signed Byte Normalised || 1 
|-
|Unsigned Byte || 2 
|-
|Signed Byte || 3 
|-
|Unsigned Short Normalised || 4 
|-
|Signed Short Normalised || 5 
|-
|Unsigned Short || 6 
|-
|Signed Short || 7 
|-
|Unsigned Integer Normalised || 8 
|-
|Signed Integer Normalised || 9 
|-
|Unsigned Integer || 10 
|-
|Signed Integer || 11 
|-
|Float || 12 
|-
|}

=== Meta Data Format ===

{| class="wikitable" style="text-align: center;"
|-
| style="background-color:#505652; color:#FFFFFF;" |'''FourCC'''<br />4 bytes
| style="background-color:#505652; color:#FFFFFF;" |'''Key'''<br />4 bytes
| style="background-color:#505652; color:#FFFFFF;" |'''Data Size'''<br />4 bytes
| style="background-color:#505652; color:#FFFFFF;" |'''Data'''<br />variable
| style="background-color:#505652; color:#FFFFFF;" |'''Padding'''<br />variable
|-
|}

==== FourCC ====

is a four byte identifier (consisting of single byte characters or integers) whose value, combined with the value of ‘Key’, is used to determine how ‘Data’ should be handled.<br />
The values {‘P’, ‘V’, ‘R’, 0} to {‘P’, ‘V’, ‘R’, 255} (and their numerical equivalents) are reserved and must not be used except as described in Pre-defined Medata Data section.<br />

==== Pre-defined Medata Data ====

{| class="wikitable" style="text-align: center;"
|-
| style="background-color:#505652; color:#FFFFFF;" |'''FourCC'''
| style="background-color:#505652; color:#FFFFFF;" |'''Key'''
| style="background-color:#505652; color:#FFFFFF;" |'''Data Size'''
| style="background-color:#505652; color:#FFFFFF;" |'''Data Description'''
|-
|colspan="5" style="text-align:center; background-color:lightblue;" | <span style="color:black;">Pre-defined metadata</span>
|-
| ‘P’, ‘V’, ‘R’, 3 || 0 || Variable ||  An array of integers describing the position and sizes of each texture within a texture atlas.<br /> <small>Each sequence of four integers represents the information for a single texture within the atlas and appear in the order:</small>  
1. X Position 
2. Y Position 
3. Width 
4. Height
|-
| ‘P’, ‘V’, ‘R’, 3 || 1 || 8 || Specifies that the file contains normal map information.<br /> 
<small>
The 8 bytes are in the form of a 32bit float representing the scale of the normal map, followed by a four character array describing the order of the channels,<br /> for example {‘x’, ‘y’, ‘z’, ‘h’}. Use of ‘h’ as the representation for a given channel denotes that the channel in question contains the original height map.
<small>
|-
| ‘P’, ‘V’, ‘R’, 3 || 2 || 6 || Specifies that the file contains a cube map and the order of the faces within that cube map.<br />  
<small>
The 6 bytes represent a six character string. This string shows the order the cube map faces are stored in the texture data, for example ‘XxYyZz’.<br />
Uppercase letters refer to a positive axis position while lowercase refer to a negative axis position. Not all axes must be present.
<small>
|-
| ‘P’, ‘V’, ‘R’, 3 || 3 || 3 || Specifies the logical orientation of the texture within the texture data.<br />
<small>
This does not affect the mapping from pixels to texture coordinates. Each byte is a Boolean value representing the orientation for a single axis in the order X, Y, Z.<br />
The values are as follows:
<small>
*X Axis Non-zero value = values increase to the left , Zero value = X values increase to the right 
*Y Axis Non-zero value = Y values increase upwards , Zero value = Y values increase downwards 
*Z Axis Non-zero value = Z values increase outwards , Zero value = Z values increase inwards 
|-
| ‘P’, ‘V’, ‘R’, 3 || 4 || 12 || Specifies whether the texture has a border.<br />
<small>
The 12 bytes are broken down into three unsigned 32bit integers. The three integers represent the size of the border of the image, in pixels, on the X, Y and Z axes, respectively.<br /> These values are used to offset texture reads by the size of the border in order to obtain the actual texture data.
<br />It should be noted that only three border sizes are given, this means that the border size for X is applied to both the left and right of the image, Y to the top and bottom and Z to the front and back.
</small>
|-
| ‘P’, ‘V’, ‘R’, 3 || 5 || variable || Specifies that this block contains padding data.<br />
<small>
The size of data varies in order to align the texture data with a convenient block boundary.<br />
The contents of data are left undefined. This block should be skipped during parsing.<br />
</small>
|-
|}

==== Key ====

is an unsigned 32bit integer, which, when coupled with ‘FourCC’ determines how ‘Data’ should be handled.

==== Data Size ====

is an unsigned 32bit integer representing the size of ‘Data’ in bytes.

==== Data ====

is an array of user defined information of size determined from ‘Data Size’ of a data type and purpose determined from the value of ‘FourCC’ and ‘Key’.

==== Padding ====

8 bytes or more, if defined.

=== Texture Data ===

*http://web.onetel.net.uk/~simonnihal/assorted3d/fenney03texcomp.pdf PVRTC algorithm: Texture Compression using Low-Frequency Signal Modulation
*http://blog.imgtec.com/powervr/understanding-powervr-series5xt-pvrtc-pvrtc2-and-texture-compression-part-6 overview

== Tools ==

*http://community.imgtec.com/developers/powervr/tools/ suite of utilities and docs

== Related Articles ==

*[[GXT|.gxt]] Graphic texture files