svgo --precision

CHANGELOG.markdown

@@ -2,6 +2,8 @@
 
 ## unreleased
 
+* Added `svgo-allow-lossy` and `svgo-precision` options to use svgo in lossy mode. This sets svgo `precision`, which can result in substantially smaller svgs. Lower values are more lossy. 3 is the default, but many SVGs will work well even with 0 or 1. [#210] [@gurgeous](https://github.com/gurgeous)
+
 ## v0.31.3 (2023-02-17)
 
 * Support Psych4/Ruby 3.1 changes to use safe_yaml methods by default [#203](https://github.com/toy/image_optim/issues/203) [#204](https://github.com/toy/image_optim/pull/204) [@oscillot](https://github.com/oscillot) [@toy](https://github.com/toy)

lib/image_optim/worker/svgo.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require 'image_optim/option_helpers'
 require 'image_optim/worker'
 
 class ImageOptim
@@ -16,6 +17,24 @@ class Svgo < Worker
         Array(v).map(&:to_s)
       end
 
+      ALLOW_LOSSY_OPTION =
+      option(:allow_lossy, false, 'Allow precision option'){ |v| !!v }
+
+      PRECISION_OPTION =
+      option(:precision, 3, 'number of digits in the fractional part ' \
+                            '`0`..`10`, ignored in default/lossless mode') \
+                            do |v, opt_def|
+        if allow_lossy
+          OptionHelpers.limit_with_range(v.to_i, 0..10)
+        else
+          if v != opt_def.default
+            warn "#{self.class.bin_sym} #{opt_def.name} #{v} ignored " \
+                 'in default/lossless mode'
+          end
+          opt_def.default
+        end
+      end
+
       def optimize(src, dst, options = {})
         args = %W[
           --input #{src}
@@ -27,6 +46,7 @@ def optimize(src, dst, options = {})
         enable_plugins.each do |plugin_name|
           args.unshift "--enable=#{plugin_name}"
         end
+        args.unshift "--precision=#{precision}" if allow_lossy
         execute(:svgo, args, options) && optimized?(src, dst)
       end
     end

spec/image_optim/worker/svgo_spec.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'image_optim/worker/svgo'
+
+describe ImageOptim::Worker::Svgo do
+  describe 'precision option' do
+    describe 'default' do
+      subject{ described_class::PRECISION_OPTION.default }
+
+      it{ is_expected.to eq(3) }
+    end
+
+    describe 'value' do
+      let(:subject){ described_class.new(ImageOptim.new, options).precision }
+
+      context 'when lossy not allowed' do
+        context 'by default' do
+          let(:options){ {} }
+
+          it{ is_expected.to eq(3) }
+        end
+
+        context 'when value is passed through options' do
+          let(:options){ {precision: 5} }
+
+          it 'warns and keeps default' do
+            expect_any_instance_of(described_class).
+              to receive(:warn).with(%r{ignored in default/lossless mode})
+            is_expected.to eq(3)
+          end
+        end
+      end
+
+      context 'when lossy allowed' do
+        context 'by default' do
+          let(:options){ {allow_lossy: true} }
+
+          it{ is_expected.to eq(3) }
+        end
+
+        context 'when value is passed through options' do
+          let(:options){ {allow_lossy: true, precision: 5} }
+
+          it 'sets the value without warning' do
+            expect_any_instance_of(described_class).not_to receive(:warn)
+            is_expected.to eq(5)
+          end
+        end
+      end
+    end
+  end
+end