Add PngDecoder::gamma_value method #2007
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anforowicz
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Sep 19, 2023
src/codecs/png.rs
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| /// > the values given above as if they had appeared in gAMA and cHRM chunks. | ||
| pub fn gamma_value(&self) -> ImageResult<Option<f64>> { | ||
| let gamma = if self.reader.info().srgb.is_some() { | ||
| Some(0.45455) |
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I wonder why you have chosen to manually consider srgb and gama_chunk, instead of using Info::source_gamma, which AFAICT takes both srgb (here) and gama_chunk (here) into account. FWIW, png::srgb::substitute_gamma is also 45455
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That's a good point point... I didn't notice the png crate already implemented that logic
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Thanks - LGTM! |
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The
Resultreturn type was chosen so that the method can return I/O errors once the PNG decoder no longer reads all metadata in thenew()method. And anf64was used so that all gamma values can be exactly represented (PNG encodes the value as a fixed precision decimal stored as a u32 which doesn't directly map to a f32).cc: @anforowicz
Fixes #2001