From eec5647b4bb8461f34c203f7d13e6ed10e15eecb Mon Sep 17 00:00:00 2001
From: Ishotihadus <hanachan.pao@gmail.com>
Date: Sat, 3 Mar 2018 16:29:10 +0900
Subject: [PATCH] Add DXT1 Support

---
 lib/mikunyan/decoders/dxtc_block_decoder.rb | 37 +++++++++++++++++++++
 lib/mikunyan/decoders/image_decoder.rb      | 16 +++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 lib/mikunyan/decoders/dxtc_block_decoder.rb

diff --git a/lib/mikunyan/decoders/dxtc_block_decoder.rb b/lib/mikunyan/decoders/dxtc_block_decoder.rb
new file mode 100644
index 0000000..4ea7090
--- /dev/null
+++ b/lib/mikunyan/decoders/dxtc_block_decoder.rb
@@ -0,0 +1,37 @@
+require 'bin_utils'
+require 'fiddle'
+
+module Mikunyan
+    module DecodeHelper
+        # Module for decoding DXTC block
+        module DxtcBlockDecoder
+            def self.decode_dxt1_block(bin)
+                c0 = BinUtils.get_int16_le(bin, 0)
+                c1 = BinUtils.get_int16_le(bin, 2)
+                color = [get_rgb565(c0), get_rgb565(c1), nil, nil]
+                if c0 > c1
+                    color[2] = [(color[0][0] * 2 + color[1][0]) / 3, (color[0][1] * 2 + color[1][1]) / 3, (color[0][2] * 2 + color[1][2]) / 3, 255]
+                    color[3] = [(color[0][0] + color[1][0] * 2) / 3, (color[0][1] + color[1][1] * 2) / 3, (color[0][2] + color[1][2] * 2) / 3, 255]
+                else
+                    color[2] = [(color[0][0] + color[1][0]) / 2, (color[0][1] + color[1][1]) / 2, (color[0][2] + color[1][2]) / 2, 255]
+                    color[3] = [0, 0, 0, 0]
+                end
+                color.map!{|e| e.pack('C4')}
+                code = BinUtils.get_int32_le(bin, 4)
+                mem = String.new(capacity: 64)
+                16.times do
+                    mem << color[code & 3]
+                    code >>= 2
+                end
+                mem
+            end
+
+            def self.get_rgb565(c)
+                r = (c & 0xf800) >> 8
+                g = (c & 0x07e0) >> 3
+                b = (c & 0x001f) << 3
+                [r | r >> 5, g | g >> 6, b | b >> 5, 255]
+            end
+        end
+    end
+end
diff --git a/lib/mikunyan/decoders/image_decoder.rb b/lib/mikunyan/decoders/image_decoder.rb
index 79223a7..a29dac7 100644
--- a/lib/mikunyan/decoders/image_decoder.rb
+++ b/lib/mikunyan/decoders/image_decoder.rb
@@ -1,6 +1,7 @@
 begin; require 'oily_png'; rescue LoadError; require 'chunky_png'; end
 require 'bin_utils'
 require 'mikunyan/decoders/astc_block_decoder'
+require 'mikunyan/decoders/dxtc_block_decoder'
 
 module Mikunyan
     # Class for image decoding tools
@@ -38,6 +39,8 @@ module Mikunyan
                 decode_rgb565(width, height, bin, endian)
             when 9
                 decode_r16(width, height, bin)
+            when 10
+                decode_dxt1(width, height, bin)
             when 13
                 decode_rgba4444(width, height, bin, endian)
             when 14
@@ -350,6 +353,19 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem).flip
         end
 
+        def self.decode_dxt1(width, height, bin)
+            bw = (width + 3) / 4
+            bh = (height + 3) / 4
+            ret = ChunkyPNG::Image.new(bh * 4, bw * 4)
+            bh.times do |by|
+                bw.times do |bx|
+                    block = DecodeHelper::DxtcBlockDecoder::decode_dxt1_block(bin.byteslice((bx + by * bw) * 8, 8))
+                    ret.replace!(ChunkyPNG::Image.from_rgba_stream(4, 4, block), bx * 4, by * 4)
+                end
+            end
+            ret.crop(0, 0, height, width).flip
+        end
+
         # Decode image from ETC1 compressed binary
         # @param [Integer] width image width
         # @param [Integer] height image height