Image Format

Color attachments such as colortex and shadowcolor buffers, as well as custom images and textures, store values in different formats with varying bit depth and layout.

The default format for color attachments is RGBA (which equates to RGBA8 on most systems). However, a shader pack can specify the format using the <bufferName>Format directive.

The available image formats and their meanings are described below.

Normalized

Normalized buffers store “floating point” values in a fixed range. The values are stored as integers internally, which are converted to/from floating point numbers during read/write. Any values outside the range are clamped to fit in the range.

A detailed explanation can be found on the OpenGL wiki.

Unsigned normalized formats

Unsigned normalized buffers support values from 0.0 to 1.0 (inclusive).

Image Format	Bit Depth	Pixel Format	Pixel Type	Image	Requirements
RGBA16	4×16	RGBA	UNSIGNED_SHORT	✔️
RGBA8	4×8	RGBA	UNSIGNED_BYTE	✔️
RGB10_A2	10/10/10/2	RGBA	UNSIGNED_INT_2_10_10_10_REV	✔️
RGBA4*	4×4	RGBA	UNSIGNED_SHORT_4_4_4_4_REV	❌	OpenGL 4.2+
RGB5_A1	5/5/5/1	RGBA	UNSIGNED_SHORT_1_5_5_5_REV	❌	OpenGL 4.2+
RGB16	3×16	RGB	UNSIGNED_SHORT	❌
RGB8	3×8	RGB	UNSIGNED_BYTE	❌
RGB565*	5/6/5	RGB	UNSIGNED_SHORT_5_6_5_REV	❌	OpenGL 4.1+ or ARB_ES2_compatibility
RG16	2×16	RG	UNSIGNED_SHORT	✔️
RG8	2×8	RG	UNSIGNED_BYTE	✔️
R16	1×16	RED	UNSIGNED_SHORT	✔️
R8	1×8	RED	UNSIGNED_BYTE	✔️
RGBA2*	4×2	RGBA		❌
R3_G3_B2	3/3/2	RGB	UNSIGNED_BYTE_2_3_3_REV	❌

^{*Requires Iris 1.8+}

Signed normalized formats

Signed normalized buffers support values from -1.0 to 1.0 (inclusive).

Image Format	Bit Depth	Pixel Format	Pixel Type	Image
RGBA16_SNORM	4×16	RGBA	SHORT	✔️
RGBA8_SNORM	4×8	RGBA	BYTE	✔️
RGB16_SNORM	3×16	RGB	SHORT	❌
RGB8_SNORM	3×8	RGB	BYTE	❌
RG16_SNORM	2×16	RG	SHORT	✔️
RG8_SNORM	2×8	RG	BYTE	✔️
R16_SNORM	1×16	RED	SHORT	✔️
R8_SNORM	1×8	RED	BYTE	✔️

Floating point

Floating point buffers allow the attachment to store true floating point values. They are only available with larger than default precision due to the increased storage needed for floating point values. However, they offer a significantly larger range of values, allowing the storing of HDR values.

Detailed explanation: OpenGL Wiki - Small Float Formats

Floating point formats

Image Format	Bit Depth	Pixel Format	Pixel Type	Image
RGBA32F	4×32	RGBA	FLOAT	✔️
RGBA16F	4×16	RGBA	HALF_FLOAT	✔️
RGB32F	3×32	RGB	FLOAT	❌
RGB16F	3×16	RGB	HALF_FLOAT	❌
R11F_G11F_B10F	11/11/10	RGB	UNSIGNED_INT_10F_11F_11F_REV*	✔️
RGB9_E5	Special	RGB	UNSIGNED_INT_5_9_9_9_REV*	❌
RG32F	2×32	RG	FLOAT	✔️
RG16F	2×16	RG	HALF_FLOAT	✔️
R32F	1×32	RED	FLOAT	✔️
R16F	1×16	RED	HALF_FLOAT	✔️

^{*Requires Iris 1.8+}

The RGB9_E5 format uses a 5-bit exponent for all three terms (R, G, and B), where each component has a 9 bit mantissa. This allows for significantly more precision than R11F_G11F_B10F, which only has 6 to 5 bits of precision per component. However, R11F_G11F_B10F has individual exponents for each component. In both cases, there is no sign bit, so these formats cannot store negative values.

Integral

Bit Depth	Signed Min	Signed Max	Unsigned Max
32	-2147483648	2147483647	4294967295
10	-512	511	1023
16	-32768	32767	65535
8	-128	127	255
2	-2	1	3

Unsigned integral formats

Unsigned integral buffers store unsigned integers, which will not be interpreted as negative values (although they can be cast to signed integers after being read). As such they do not directly allow the storage of negative integers, but have double the range of their signed cousins in the positive domain.

Image Format	Bit Depth	Pixel Format	Pixel Type	Image
RGBA32UI	4×32	RGBA_INTEGER	UNSIGNED_INT	✔️
RGBA16UI	4×16	RGBA_INTEGER	UNSIGNED_SHORT	✔️
RGBA8UI	4×8	RGBA_INTEGER	UNSIGNED_BYTE	✔️
RGB10_A2UI*	10/10/10/2	RGBA_INTEGER	UNSIGNED_INT_2_10_10_10_REV	✔️
RGB32UI	3×32	RGB_INTEGER	UNSIGNED_INT	❌
RGB16UI	3×16	RGB_INTEGER	UNSIGNED_SHORT	❌
RGB8UI	3×8	RGB_INTEGER	UNSIGNED_BYTE	❌
RG32UI	2×32	RG_INTEGER	UNSIGNED_INT	✔️
RG16UI	2×16	RG_INTEGER	UNSIGNED_SHORT	✔️
RG8UI	2×8	RG_INTEGER	UNSIGNED_BYTE	✔️
R32UI	1×32	RED_INTEGER	UNSIGNED_INT	✔️
R16UI	1×16	RED_INTEGER	UNSIGNED_SHORT	✔️
R8UI	1×8	RED_INTEGER	UNSIGNED_BYTE	✔️

^{*Requires Iris 1.8+}

Signed integral formats

Signed integral buffers store signed integers, just like the tin says. These are standard two’s complement integers, which means they can store negative values.

Image Format	Bit Depth	Pixel Format	Pixel Type	Image
RGBA32I	4×32	RGBA_INTEGER	INT	✔️
RGBA16I	4×16	RGBA_INTEGER	SHORT	✔️
RGBA8I	4×8	RGBA_INTEGER	BYTE	✔️
RGB32I	3×32	RGB_INTEGER	INT	❌
RGB16I	3×16	RGB_INTEGER	SHORT	❌
RGB8I	3×8	RGB_INTEGER	BYTE	❌
RG32I	2×32	RG_INTEGER	INT	✔️
RG16I	2×16	RG_INTEGER	SHORT	✔️
RG8I	2×8	RG_INTEGER	BYTE	✔️
R32I	1×32	RED_INTEGER	INT	✔️
R16I	1×16	RED_INTEGER	SHORT	✔️
R8I	1×8	RED_INTEGER	BYTE	✔️

Additional pixel types

The shader loader supports some additional pixel types, not directly associated with specific image formats, that can be used when loading raw custom textures. See the OpenGL Wiki for more information about these.

Pixel Type
UNSIGNED_BYTE_3_3_2
UNSIGNED_SHORT_5_6_5
UNSIGNED_SHORT_4_4_4_4
UNSIGNED_SHORT_5_5_5_1
UNSIGNED_INT_8_8_8_8
UNSIGNED_INT_8_8_8_8_REV
UNSIGNED_INT_10_10_10_2

Further reading

• OpenGL Wiki - Image Format
• OpenGL Wiki - Normalized Integer