Graphics Reference
In-Depth Information
(continued)
width
the width of the image in pixels.
the height of the image in pixels.
height
(
glCompressedTexImage3D
only) the depth of the
image in pixels (or number of slices for a 2D texture
array).
depth
this parameter is ignored in OpenGL ES; it was
kept for compatibility with the desktop OpenGL
interface. Should be 0.
border
the size of the image in bytes.
imageSize
contains the actual compressed pixel data for the
image; must hold
imageSize
number of bytes.
data
The standard ETC compressed texture formats supported by OpenGL ES
3.0 are listed in Table 9-12. All of the ETC formats store compressed image
data in 4 × 4 blocks. Table 9-12 lists the number of bits per pixel in each
of the ETC formats. The size of an individual ETC image can be computed
from the bits-per-pixel (bpp) ratio as follows:
sizeInBytes = max(width, 4) * max(height, 4) * bpp/8
Table 9-12
Standard Texture Compression Formats
Size (bits
per pixel)
internalFormat
Description
GL_COMPRESSED_R11_EAC
4
Single-channel unsigned
compressed
GL_RED
format
GL_COMPRESSED_SIGNED_R11_EAC
4
Single-channel signed compressed
GL_RED
format
GL_COMPRESSED_RG11_EAC
8
Two-channel unsigned compressed
GL_RG
format
GL_COMPRESSED_SIGNED_ RG11_EAC
8
Two-channel signed compressed
GL_RG
format
GL_COMPRESSED_RGB8_ETC2
4
Three-channel unsigned
compressed
GL_RGB
format
GL_COMPRESSED_SRGB8_ETC2
4
Three-channel unsigned
compressed
GL_RGB
format in
sRGB colorspace
