updated minimum rust to 1.64 to support stabilized NonZeroU32::unsign…

…ed_abs. This has a significant speed impact on leading zero calc on x86

.github/workflows/rust.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: ["1.61.0", stable, beta, nightly]
+        rust: ["1.64.0", stable, beta, nightly]
         features: [gif, jpeg, png, tiff, ico, pnm, tga, webp, bmp, hdr, dxt, dds, farbfeld, openexr, jpeg_rayon, webp-encoder, '']
     steps:
     - uses: actions/checkout@v2

Cargo.toml

@@ -5,7 +5,7 @@ edition = "2018"
 resolver = "2"
 
 # note: when changed, also update test runner in `.github/workflows/rust.yml`
-rust-version = "1.61.0"
+rust-version = "1.64.0"
 
 license = "MIT"
 description = "Imaging library written in Rust. Provides basic filters and decoders for the most common image formats."

src/codecs/jpeg/encoder.rs

@@ -763,7 +763,7 @@ fn build_quantization_segment(m: &mut Vec<u8>, precision: u8, identifier: u8, qt
 fn encode_coefficient(coefficient: i32) -> (u8, u16) {
     // since this is inlined, in the main AC case the compiler figures out that coefficient cannot be zero, so BSR on x86 doesn't need a branch
     if let Some(nz) = NonZeroI32::new(coefficient) {
-        let leading_zeros = nz.abs().leading_zeros() as u8;
+        let leading_zeros = nz.unsigned_abs().leading_zeros() as u8;
 
         // first shift right signed by 31 to make everything 1 if negative,
         // then shift right unsigned to make the leading bits 0