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Fix typos and improve wording in README.md

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grammar fix
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Rich Geldreich
2026-01-19 04:12:13 -05:00
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@@ -71,7 +71,7 @@ UASTC HDR 4x4, ASTC HDR 6x6, and UASTC HDR 6x6 files can be transcoded to:
Supported Texture Compression/Supercompression Modes
----------------------------------------------------
1. **[ETC1S](https://github.com/BinomialLLC/basis_universal/wiki/.basis-File-Format-and-ETC1S-Texture-Video-Specification)**: A roughly .3-3bpp low to medium quality supercompressed mode based off a subset of [ETC1](https://en.wikipedia.org/wiki/Ericsson_Texture_Compression) called "ETC1S". This mode supports variable quality vs. file size levels (like JPEG), alpha channels, built-in compression, and texture arrays optionally compressed as a video sequence using skip blocks ([Conditional Replenishment](https://en.wikipedia.org/wiki/MPEG-1)). This mode can be rapidly transcoded to all of the supported LDR texture formats.
1. **[ETC1S](https://github.com/BinomialLLC/basis_universal/wiki/.basis-File-Format-and-ETC1S-Texture-Video-Specification)**: A roughly .3-3bpp low to medium quality supercompressed mode based on a subset of [ETC1](https://en.wikipedia.org/wiki/Ericsson_Texture_Compression) called "ETC1S". This mode supports variable quality vs. file size levels (like JPEG), alpha channels, built-in compression, and texture arrays optionally compressed as a video sequence using skip blocks ([Conditional Replenishment](https://en.wikipedia.org/wiki/MPEG-1)). This mode can be rapidly transcoded to all of the supported LDR texture formats.
2. **[UASTC LDR 4x4](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-LDR-4x4-Texture-Specification)**: An 8 bits/pixel LDR high quality mode. UASTC LDR is a 19 mode subset of the standard [ASTC LDR](https://en.wikipedia.org/wiki/Adaptive_scalable_texture_compression) 4x4 (8bpp) texture format, but with a custom block format containing transcoding hints. Transcoding UASTC LDR to ASTC LDR and BC7 are particularly fast and simple, because UASTC LDR is a common subset of both BC7 and ASTC. The transcoders for the other texture formats are accelerated by several format-specific hint bits present in each UASTC LDR block.
@@ -266,7 +266,7 @@ Be aware that the .EXR reader we're using is [TinyEXR's](https://github.com/syoy
Alternatively, LDR images (such as .PNG) can be compressed to an HDR format by specifying `-hdr`, `-hdr_6x6`, or `-hdr_6x6i`. By default LDR images, when compressed to an HDR format, are first upconverted to HDR by converting them from sRGB to linear light and scaled to 100 [nits](https://en.wikipedia.org/wiki/Candela_per_square_metre) (candelas per square meter). The sRGB conversion step can be disabled by specifying `-hdr_ldr_no_srgb_to_linear`, and the normalized RGB linear light to nit multiplier can be changed by specifying `-hdr_ldr_upconversion_nit_multiplier X`.
Note: If you're compressing LDR/SDR image files to an HDR format, the codec's default behavior is to convert the 8-bit image data to linear light (by undoing the sRGB transfer function). It then multiplies the linear light RGB values by the LDR->HDR upconversion multiplier, which is in [nits (candela per sq. meter)](https://en.wikipedia.org/wiki/Candela_per_square_metre). In previous versions of the codec, this multiplier was effectively 1 nit, but it now defaults to 100 nits in all modes. (The typical luminance of LDR monitors is 80-100 nits.) To change this, use the "-hdr_ldr_upconversion_nit_multiplier X" command line option. (This is done because the HDR 6x6 codecs function internally in the [ICtCp HDR colorspace](https://en.wikipedia.org/wiki/ICtCp). LDR/SDR images must be upconverted to linear light HDR images scaled to a proper max. luminance based off how the image data will be displayed on actual SDR/HDR monitors.)
Note: If you're compressing LDR/SDR image files to an HDR format, the codec's default behavior is to convert the 8-bit image data to linear light (by undoing the sRGB transfer function). It then multiplies the linear light RGB values by the LDR->HDR upconversion multiplier, which is in [nits (candela per sq. meter)](https://en.wikipedia.org/wiki/Candela_per_square_metre). In previous versions of the codec, this multiplier was effectively 1 nit, but it now defaults to 100 nits in all modes. (The typical luminance of LDR monitors is 80-100 nits.) To change this, use the "-hdr_ldr_upconversion_nit_multiplier X" command line option. (This is done because the HDR 6x6 codecs function internally in the [ICtCp HDR colorspace](https://en.wikipedia.org/wiki/ICtCp). LDR/SDR images must be upconverted to linear light HDR images scaled to a proper max. luminance based on how the image data will be displayed on actual SDR/HDR monitors.)
### Some Useful Command Line Options