diff --git a/.github/workflows/autosquash.yml b/.github/workflows/autosquash.yml
deleted file mode 100644
index a898991c..00000000
--- a/.github/workflows/autosquash.yml
+++ /dev/null
@@ -1,39 +0,0 @@
-name: Autosquash
-on:
-  check_run:
-    types:
-      # Check runs completing successfully can unblock the
-      # corresponding pull requests and make them mergeable.
-      - completed
-  pull_request:
-    types:
-      # A closed pull request makes the checks on the other
-      # pull request on the same base outdated.
-      - closed
-      # Adding the autosquash label to a pull request can
-      # trigger an update or a merge.
-      - labeled
-  pull_request_review:
-    types:
-      # Review approvals can unblock the pull request and
-      # make it mergeable.
-      - submitted
-  # Success statuses can unblock the corresponding
-  # pull requests and make them mergeable.
-  status: {}
-
-jobs:
-  autosquash:
-    name: Autosquash
-    runs-on: ubuntu-18.04
-    steps:
-      - uses: tibdex/autosquash@v2
-        with:
-          # We can't use the built-in secrets.GITHUB_TOKEN yet because of this limitation:
-          # https://github.community/t5/GitHub-Actions/Triggering-a-new-workflow-from-another-workflow/td-p/31676
-          # In the meantime, use a token granting write access on the repo:
-          # - a GitHub App token
-          #   See https://github.com/marketplace/actions/github-app-token.
-          # - a personal access token
-          #   See https://help.github.com/en/articles/creating-a-personal-access-token-for-the-command-line.
-          github_token: ${{ secrets.AUTOSQUASH_TOKEN }}
diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index 5c0cf8e0..ec3680a1 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -7,22 +7,68 @@ on:
 
 jobs:
 
-  create-binaries:
+  create-windows-binaries:
 
     strategy:
       matrix:
-        os: [ubuntu-latest, macOS-latest, windows-latest]
+        conf: [x86_64, i686]
+
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Install stable
+      uses: actions-rs/toolchain@v1
+      with:
+        profile: minimal
+        toolchain: stable
+        target: ${{ matrix.conf }}-pc-windows-msvc
+        override: true
+
+    - name: Build oxipng
+      run: |
+        cargo build --release --target ${{ matrix.conf }}-pc-windows-msvc
+
+    - name: Get the version
+      shell: bash
+      id: tagName
+      run: |
+        VERSION=$(cargo pkgid | cut -d# -f2 | cut -d: -f2)
+        echo "::set-output name=tag::$VERSION"
+
+    - name: Build package
+      id: package
+      shell: bash
+      run: |
+        ARCHIVE_TARGET="${{ matrix.conf }}-pc-windows-msvc"
+        ARCHIVE_NAME="oxipng-${{ steps.tagName.outputs.tag }}-$ARCHIVE_TARGET"
+        ARCHIVE_FILE="${ARCHIVE_NAME}.zip"
+        mv LICENSE LICENSE.txt
+        7z a ${ARCHIVE_FILE} \
+             ./target/${{ matrix.conf }}-pc-windows-msvc/release/oxipng.exe \
+             ./CHANGELOG.md ./LICENSE.txt ./README.md
+        echo "::set-output name=file::${ARCHIVE_FILE}"
+        echo "::set-output name=name::${ARCHIVE_NAME}.zip"
+
+    - name: Upload artifacts
+      uses: actions/upload-artifact@v2
+      with:
+        name: ${{ steps.package.outputs.name }}
+        path: ${{ steps.package.outputs.file }}
+
+  create-unix-binaries:
+
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
         include:
           - os: ubuntu-latest
             target: x86_64-unknown-linux-musl
-          - os: macOS-latest
+          - os: macos-latest
             target: x86_64-apple-darwin
-          - os: windows-latest
-            target: x86_64-pc-windows-msvc
-          - os: windows-latest
-            target: i686-pc-windows-msvc
 
-    runs-on: '${{ matrix.os }}'
+    runs-on: ${{ matrix.os }}
 
     steps:
     - uses: actions/checkout@v2
@@ -36,19 +82,19 @@ jobs:
         override: true
 
     - name: Install musl
-      run: sudo apt-get install musl-tools
       if: contains(matrix.target, 'linux-musl')
+      run: |
+        sudo apt-get install musl-tools
 
     - name: Build oxipng
       run: |
         cargo build --release --target ${{ matrix.target }}
 
     - name: Strip binary
-      run: strip 'target/${{ matrix.target }}/release/oxipng'
-      if: "!contains(matrix.target, 'windows')"
+      run: |
+        strip target/${{ matrix.target }}/release/oxipng
 
     - name: Get the version
-      shell: bash
       id: tagName
       run: |
         VERSION=$(cargo pkgid | cut -d# -f2 | cut -d: -f2)
@@ -56,23 +102,17 @@ jobs:
 
     - name: Build package
       id: package
-      shell: bash
       run: |
-        ARCHIVE_NAME="oxipng-${{ steps.tagName.outputs.tag }}-${{ matrix.target }}"
-        if [[ '${{ matrix.target }}' == *windows* ]]; then
-          ARCHIVE_FILE="${ARCHIVE_NAME}.zip"
-          mv LICENSE LICENSE.txt
-          7z a "${ARCHIVE_FILE}" "./target/${{ matrix.target }}/release/oxipng.exe" ./CHANGELOG.md ./LICENSE.txt ./README.md
-          echo ::set-output "name=file::${ARCHIVE_FILE}"
-          echo ::set-output "name=name::${ARCHIVE_NAME}.zip"
-        else
-          ARCHIVE_FILE="${ARCHIVE_NAME}.tar.gz"
-          mkdir "/tmp/${ARCHIVE_NAME}"
-          cp README.md CHANGELOG.md LICENSE "target/${{ matrix.target }}/release/oxipng" "/tmp/${ARCHIVE_NAME}"
-          tar -czf "${PWD}/${ARCHIVE_FILE}" -C /tmp/ "${ARCHIVE_NAME}"
-          echo ::set-output "name=file::${ARCHIVE_FILE}"
-          echo ::set-output "name=name::${ARCHIVE_NAME}.tar.gz"
-        fi
+        ARCHIVE_TARGET=${{ matrix.target }}
+        ARCHIVE_NAME="oxipng-${{ steps.tagName.outputs.tag }}-$ARCHIVE_TARGET"
+        ARCHIVE_FILE="${ARCHIVE_NAME}.tar.gz"
+        mkdir "/tmp/${ARCHIVE_NAME}"
+        cp README.md CHANGELOG.md LICENSE \
+           target/${{ matrix.target }}/release/oxipng \
+           /tmp/${ARCHIVE_NAME}
+        tar -czf ${PWD}/${ARCHIVE_FILE} -C /tmp/ ${ARCHIVE_NAME}
+        echo ::set-output "name=file::${ARCHIVE_FILE}"
+        echo ::set-output "name=name::${ARCHIVE_NAME}.tar.gz"
 
     - name: Upload artifacts
       uses: actions/upload-artifact@v2
@@ -80,9 +120,10 @@ jobs:
         name: ${{ steps.package.outputs.name }}
         path: ${{ steps.package.outputs.file }}
 
+
   deploy:
 
-    needs: create-binaries
+    needs: [create-windows-binaries, create-unix-binaries]
 
     runs-on: ubuntu-latest
 
diff --git a/.github/workflows/oxipng.yml b/.github/workflows/oxipng.yml
index 14bef97c..9b21cf8f 100644
--- a/.github/workflows/oxipng.yml
+++ b/.github/workflows/oxipng.yml
@@ -19,7 +19,7 @@ jobs:
         - x86_64-apple-darwin
         toolchain:
         # Minimum stable
-        - "1.41.0"
+        - "1.45.0"
         - stable
         - beta
         - nightly
diff --git a/Cargo.lock b/Cargo.lock
index d7939e6f..16cc4827 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,618 +4,647 @@
 name = "adler"
 version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee2a4ec343196209d6594e19543ae87a39f96d5534d7174822a3ad825dd6ed7e"
 
 [[package]]
 name = "adler32"
 version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aae1277d39aeec15cb388266ecc24b11c80469deae6067e17a1a7aa9e5c1f234"
 
 [[package]]
 name = "ansi_term"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
 dependencies = [
- "winapi 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi",
 ]
 
 [[package]]
 name = "atty"
 version = "0.2.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
 dependencies = [
- "hermit-abi 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.77 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hermit-abi",
+ "libc",
+ "winapi",
 ]
 
 [[package]]
 name = "autocfg"
 version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
 [[package]]
 name = "bit-vec"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f0dc55f2d8a1a85650ac47858bb001b4c0dd73d79e3c455a842925e68d29cd3"
 
 [[package]]
 name = "bitflags"
 version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 
 [[package]]
 name = "build_const"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39092a32794787acd8525ee150305ff051b0aa6cc2abaf193924f5ab05425f39"
 
 [[package]]
 name = "bytemuck"
 version = "1.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41aa2ec95ca3b5c54cf73c91acf06d24f4495d5f1b1c12506ae3483d646177ac"
 
 [[package]]
 name = "byteorder"
 version = "1.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08c48aae112d48ed9f069b33538ea9e3e90aa263cfa3d1c24309612b1f7472de"
 
 [[package]]
 name = "cc"
-version = "1.0.60"
+version = "1.0.61"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed67cbde08356238e75fc4656be4749481eeffb09e19f320a25237d5221c985d"
 
 [[package]]
 name = "cfg-if"
 version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "chrono"
-version = "0.4.18"
+version = "0.4.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "670ad68c9088c2a963aaa298cb369688cf3f9465ce5e2d4ca10e6e0098a1ce73"
 dependencies = [
- "libc 0.2.77 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-integer 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "time 0.1.44 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc",
+ "num-integer",
+ "num-traits",
+ "time",
+ "winapi",
 ]
 
 [[package]]
 name = "clap"
 version = "2.33.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37e58ac78573c40708d45522f0d80fa2f01cc4f9b4e2bf749807255454312002"
 dependencies = [
- "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
- "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "strsim 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "unicode-width 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "vec_map 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ansi_term",
+ "atty",
+ "bitflags",
+ "strsim",
+ "textwrap",
+ "unicode-width",
+ "vec_map",
 ]
 
 [[package]]
 name = "cloudflare-zlib"
 version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f5ed63a019d55bacd15cadcbcb96bf41b16281417fff393bdb55fa84255fe4b9"
 dependencies = [
- "cloudflare-zlib-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cloudflare-zlib-sys",
 ]
 
 [[package]]
 name = "cloudflare-zlib-sys"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7e195cb274a0d6ee87e718838a09baecd7cbc9f6075dac256a84cb5842739c06"
 dependencies = [
- "cc 1.0.60 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc",
 ]
 
+[[package]]
+name = "color_quant"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d7b894f5411737b7867f4827955924d7c254fc9f4d91a6aad6b097804b1018b"
+
+[[package]]
+name = "const_fn"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c478836e029dcef17fb47c89023448c64f781a046e0300e257ad8225ae59afab"
+
 [[package]]
 name = "crc"
 version = "1.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d663548de7f5cca343f1e0a48d14dcfb0e9eb4e079ec58883b7251539fa10aeb"
 dependencies = [
- "build_const 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "build_const",
 ]
 
 [[package]]
 name = "crc32fast"
-version = "1.2.0"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "81156fece84ab6a9f2afdb109ce3ae577e42b1228441eded99bd77f627953b1a"
 dependencies = [
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 1.0.0",
 ]
 
 [[package]]
 name = "crossbeam-channel"
-version = "0.4.4"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dca26ee1f8d361640700bde38b2c37d8c22b3ce2d360e1fc1c74ea4b0aa7d775"
 dependencies = [
- "crossbeam-utils 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "maybe-uninit 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 1.0.0",
+ "crossbeam-utils",
 ]
 
 [[package]]
 name = "crossbeam-deque"
-version = "0.7.3"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94af6efb46fef72616855b036a624cf27ba656ffc9be1b9a3c931cfc7749a9a9"
 dependencies = [
- "crossbeam-epoch 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "crossbeam-utils 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "maybe-uninit 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 1.0.0",
+ "crossbeam-epoch",
+ "crossbeam-utils",
 ]
 
 [[package]]
 name = "crossbeam-epoch"
-version = "0.8.2"
+version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0f606a85340376eef0d6d8fec399e6d4a544d648386c6645eb6d0653b27d9f"
 dependencies = [
- "autocfg 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "crossbeam-utils 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "maybe-uninit 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "memoffset 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "scopeguard 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cfg-if 1.0.0",
+ "const_fn",
+ "crossbeam-utils",
+ "lazy_static",
+ "memoffset",
+ "scopeguard",
 ]
 
 [[package]]
 name = "crossbeam-utils"
-version = "0.7.2"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec91540d98355f690a86367e566ecad2e9e579f230230eb7c21398372be73ea5"
 dependencies = [
- "autocfg 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "autocfg",
+ "cfg-if 1.0.0",
+ "const_fn",
+ "lazy_static",
 ]
 
 [[package]]
 name = "deflate"
 version = "0.8.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73770f8e1fe7d64df17ca66ad28994a0a623ea497fa69486e14984e715c5d174"
 dependencies = [
- "adler32 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "byteorder 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "adler32",
+ "byteorder",
 ]
 
 [[package]]
 name = "either"
 version = "1.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
 
 [[package]]
 name = "glob"
 version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b919933a397b79c37e33b77bb2aa3dc8eb6e165ad809e58ff75bc7db2e34574"
 
 [[package]]
 name = "hashbrown"
-version = "0.9.0"
+version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7afe4a420e3fe79967a00898cc1f4db7c8a49a9333a29f8a4bd76a253d5cd04"
 
 [[package]]
 name = "hermit-abi"
-version = "0.1.16"
+version = "0.1.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aca5565f760fb5b220e499d72710ed156fdb74e631659e99377d9ebfbd13ae8"
 dependencies = [
- "libc 0.2.77 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc",
 ]
 
 [[package]]
 name = "image"
-version = "0.23.10"
+version = "0.23.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4f0a8345b33b082aedec2f4d7d4a926b845cee184cbe78b703413066564431b"
 dependencies = [
- "bytemuck 1.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "byteorder 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-iter 0.1.41 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-rational 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "png 0.16.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bytemuck",
+ "byteorder",
+ "color_quant",
+ "num-iter",
+ "num-rational",
+ "num-traits",
+ "png",
 ]
 
 [[package]]
 name = "indexmap"
 version = "1.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "55e2e4c765aa53a0424761bf9f41aa7a6ac1efa87238f59560640e27fca028f2"
 dependencies = [
- "autocfg 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "hashbrown 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "rayon 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "autocfg",
+ "hashbrown",
+ "rayon",
 ]
 
 [[package]]
 name = "itertools"
 version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "284f18f85651fe11e8a991b2adb42cb078325c996ed026d994719efcfca1d54b"
 dependencies = [
- "either 1.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "either",
 ]
 
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.77"
+version = "0.2.80"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d58d1b70b004888f764dfbf6a26a3b0342a1632d33968e4a179d8011c760614"
 
 [[package]]
 name = "libdeflate-sys"
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diff --git a/Cargo.toml b/Cargo.toml
index 54971d47..634b4e9e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,17 +33,17 @@ bit-vec = "^0.6.2"
 byteorder = "^1.0.0"
 crc = "^1.2.0"
 itertools = "^0.9.0"
-zopfli = "^0.4.0"
+zopfli = { version = "^0.4.0", optional = true }
 miniz_oxide = "0.4"
 rgb = "0.8.25"
 indexmap = "1.6.0"
-libdeflater = "0.5.0"
+libdeflater = { version = "0.5.0", optional = true }
 log = "0.4.11"
 stderrlog = { version = "0.5.0", optional = true }
 
 [dependencies.rayon]
 optional = true
-version = "^1.4.0"
+version = "^1.5.0"
 
 [dependencies.clap]
 optional = true
@@ -63,7 +63,7 @@ features = ["arm-always"]
 version = "^0.2.2"
 
 [build-dependencies]
-rustc_version = "0.2"
+rustc_version = "0.3"
 
 [features]
 binary = [
@@ -71,7 +71,7 @@ binary = [
     "wild",
     "stderrlog",
 ]
-default = ["binary", "parallel"]
+default = ["binary", "parallel", "libdeflater", "zopfli"]
 parallel = ["rayon", "indexmap/rayon"]
 
 [lib]
diff --git a/README.md b/README.md
index 31c6ca2d..be6df962 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ cargo build --release
 cp target/release/oxipng /usr/local/bin
 ```
 
-The current minimum supported Rust version is **1.41.0**.
+The current minimum supported Rust version is **1.47.0**.
 
 Oxipng follows Semantic Versioning.
 
diff --git a/README.template.md b/README.template.md
index 8f3ba013..e7a85cfa 100644
--- a/README.template.md
+++ b/README.template.md
@@ -30,7 +30,7 @@ cargo build --release
 cp target/release/oxipng /usr/local/bin
 ```
 
-The current minimum supported Rust version is **1.41.0**.
+The current minimum supported Rust version is **1.47.0**.
 
 Oxipng follows Semantic Versioning.
 
diff --git a/src/atomicmin.rs b/src/atomicmin.rs
index 0d867fc3..af2287a9 100644
--- a/src/atomicmin.rs
+++ b/src/atomicmin.rs
@@ -1,5 +1,5 @@
 use std::sync::atomic::AtomicUsize;
-use std::sync::atomic::Ordering::{Relaxed, SeqCst};
+use std::sync::atomic::Ordering::SeqCst;
 
 #[derive(Debug)]
 pub struct AtomicMin {
@@ -28,18 +28,6 @@ impl AtomicMin {
     }
 
     pub fn set_min(&self, new_val: usize) {
-        let mut current_val = self.val.load(Relaxed);
-        loop {
-            if new_val < current_val {
-                if let Err(v) = self
-                    .val
-                    .compare_exchange(current_val, new_val, SeqCst, Relaxed)
-                {
-                    current_val = v;
-                    continue;
-                }
-            }
-            break;
-        }
+        self.val.fetch_min(new_val, SeqCst);
     }
 }
diff --git a/src/deflate/mod.rs b/src/deflate/mod.rs
index d64b958b..69879901 100644
--- a/src/deflate/mod.rs
+++ b/src/deflate/mod.rs
@@ -3,12 +3,13 @@ use crate::error::PngError;
 use crate::Deadline;
 use crate::PngResult;
 use indexmap::IndexSet;
-use std::cmp::max;
 
 #[doc(hidden)]
 pub mod miniz_stream;
 
+#[cfg(feature = "libdeflater")]
 mod deflater;
+#[cfg(feature = "libdeflater")]
 pub use deflater::deflate as libdeflater_deflate;
 
 #[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
@@ -47,7 +48,10 @@ pub fn deflate(
     miniz_stream::compress_to_vec_oxipng(data, zc, zw.into(), zs.into(), max_size, deadline)
 }
 
+#[cfg(feature = "zopfli")]
 pub fn zopfli_deflate(data: &[u8]) -> PngResult<Vec<u8>> {
+    use std::cmp::max;
+
     let mut output = Vec::with_capacity(max(1024, data.len() / 20));
     let options = zopfli::Options::default();
     match zopfli::compress(&options, &zopfli::Format::Zlib, data, &mut output) {
@@ -79,8 +83,10 @@ pub enum Deflaters {
         /// Default: `15`
         window: u8,
     },
+    #[cfg(feature = "zopfli")]
     /// Use the better but slower Zopfli implementation
     Zopfli,
+    #[cfg(feature = "libdeflater")]
     /// Use libdeflater.
     Libdeflater,
 }
diff --git a/src/lib.rs b/src/lib.rs
index d988e471..081d1a60 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,6 +12,11 @@
 #![warn(clippy::path_buf_push_overwrite)]
 #![warn(clippy::range_plus_one)]
 #![allow(clippy::cognitive_complexity)]
+#![cfg_attr(
+    not(any(feature = "libdeflater", feature = "zopfli")),
+    allow(irrefutable_let_patterns),
+    allow(unreachable_patterns)
+)]
 
 #[cfg(feature = "parallel")]
 extern crate rayon;
@@ -569,7 +574,9 @@ fn optimize_png(
                     &best_size,
                     &deadline,
                 ),
+                #[cfg(feature = "zopfli")]
                 Deflaters::Zopfli => deflate::zopfli_deflate(filtered),
+                #[cfg(feature = "libdeflater")]
                 Deflaters::Libdeflater => deflate::libdeflater_deflate(filtered, &best_size),
             };
 
diff --git a/src/png/mod.rs b/src/png/mod.rs
index ee425ae6..f2aa30b9 100644
--- a/src/png/mod.rs
+++ b/src/png/mod.rs
@@ -10,7 +10,7 @@ use indexmap::IndexMap;
 use rgb::ComponentSlice;
 use rgb::RGBA8;
 use std::fs::File;
-use std::io::{Read, Seek, SeekFrom};
+use std::io::{BufReader, Read};
 use std::iter::Iterator;
 use std::path::Path;
 use std::sync::Arc;
@@ -62,25 +62,24 @@ impl PngData {
     }
 
     pub fn read_file(filepath: &Path) -> Result<Vec<u8>, PngError> {
-        let mut file = match File::open(filepath) {
+        let file = match File::open(filepath) {
             Ok(f) => f,
             Err(_) => return Err(PngError::new("Failed to open file for reading")),
         };
+        let file_len = file.metadata().map(|m| m.len() as usize).unwrap_or(0);
+        let mut reader = BufReader::new(file);
         // Check file for PNG header
         let mut header = [0; 8];
-        if file.read_exact(&mut header).is_err() {
+        if reader.read_exact(&mut header).is_err() {
             return Err(PngError::new("Not a PNG file: too small"));
         }
         if !file_header_is_valid(&header) {
             return Err(PngError::new("Invalid PNG header detected"));
         }
-        if file.seek(SeekFrom::Start(0)).is_err() {
-            return Err(PngError::new("Failed to read from file"));
-        }
         // Read raw png data into memory
-        let mut byte_data: Vec<u8> =
-            Vec::with_capacity(file.metadata().map(|m| m.len() as usize).unwrap_or(0));
-        match file.read_to_end(&mut byte_data) {
+        let mut byte_data: Vec<u8> = Vec::with_capacity(file_len);
+        byte_data.extend_from_slice(&header);
+        match reader.read_to_end(&mut byte_data) {
             Ok(_) => (),
             Err(_) => return Err(PngError::new("Failed to read from file")),
         }
diff --git a/src/reduction/alpha.rs b/src/reduction/alpha.rs
index 8412aba1..cd25a81a 100644
--- a/src/reduction/alpha.rs
+++ b/src/reduction/alpha.rs
@@ -64,9 +64,7 @@ fn reduced_alpha_to_black(png: &PngImage, bpc: usize, bpp: usize) -> Vec<u8> {
         reduced.push(line.filter);
         for pixel in line.data.chunks(bpp) {
             if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
-                for _ in 0..bpp {
-                    reduced.push(0);
-                }
+                reduced.resize(reduced.len() + bpp, 0);
             } else {
                 reduced.extend_from_slice(pixel);
             }
@@ -81,12 +79,8 @@ fn reduced_alpha_to_white(png: &PngImage, bpc: usize, bpp: usize) -> Vec<u8> {
         reduced.push(line.filter);
         for pixel in line.data.chunks(bpp) {
             if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
-                for _ in 0..(bpp - bpc) {
-                    reduced.push(255);
-                }
-                for _ in 0..bpc {
-                    reduced.push(0);
-                }
+                reduced.resize(reduced.len() + bpp - bpc, 255);
+                reduced.resize(reduced.len() + bpc, 0);
             } else {
                 reduced.extend_from_slice(pixel);
             }
@@ -109,9 +103,7 @@ fn reduced_alpha_to_up(png: &PngImage, bpc: usize, bpp: usize) -> Vec<u8> {
         for (pixel, last_pixel) in line.data.chunks(bpp).zip(last_line.chunks(bpp)) {
             if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
                 current_line.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
-                for _ in 0..bpc {
-                    current_line.push(0);
-                }
+                current_line.resize(current_line.len() + bpc, 0);
             } else {
                 current_line.extend_from_slice(pixel);
             }
@@ -134,9 +126,7 @@ fn reduced_alpha_to_down(png: &PngImage, bpc: usize, bpp: usize) -> Vec<u8> {
         for (pixel, last_pixel) in line.data.chunks(bpp).zip(last_line.chunks(bpp)) {
             if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
                 reduced.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
-                for _ in 0..bpc {
-                    reduced.push(0);
-                }
+                reduced.resize(reduced.len() + bpc, 0);
             } else {
                 reduced.extend_from_slice(pixel);
             }
@@ -154,9 +144,7 @@ fn reduced_alpha_to_left(png: &PngImage, bpc: usize, bpp: usize) -> Vec<u8> {
         for pixel in line.data.chunks(bpp).rev() {
             if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
                 line_bytes.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
-                for _ in 0..bpc {
-                    line_bytes.push(0);
-                }
+                line_bytes.resize(line_bytes.len() + bpc, 0);
             } else {
                 line_bytes.extend_from_slice(pixel);
             }
@@ -176,9 +164,7 @@ fn reduced_alpha_to_right(png: &PngImage, bpc: usize, bpp: usize) -> Vec<u8> {
         for pixel in line.data.chunks(bpp) {
             if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
                 reduced.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
-                for _ in 0..bpc {
-                    reduced.push(0);
-                }
+                reduced.resize(reduced.len() + bpc, 0);
             } else {
                 reduced.extend_from_slice(pixel);
             }