Add DXT5 Support

lib/mikunyan/decoders/dxtc_block_decoder.rb

@@ -8,7 +8,7 @@ module Mikunyan
             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]
+                color = [get_rgb565a(c0), get_rgb565a(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]
@@ -26,7 +26,59 @@ module Mikunyan
                 mem
             end
 
+            def self.decode_dxt5_block(bin)
+                alpha_list, alpha_code = decode_dxt5_alpha(bin)
+                color_list, color_code = decode_dxtc_rgb(bin)
+                mem = String.new(capacity: 64)
+                16.times do
+                    mem << color_list[color_code & 3]
+                    mem << alpha_list[alpha_code & 7]
+                    color_code >>= 2
+                    alpha_code >>= 3
+                end
+                mem
+            end
+
+            def self.decode_dxtc_rgb(bin)
+                c0 = BinUtils.get_int16_le(bin, 8)
+                c1 = BinUtils.get_int16_le(bin, 10)
+                color = [get_rgb565(c0), get_rgb565(c1), nil, nil]
+                if c0 > c1
+                    color[2] = (0...3).map{|i| (color[0][i] * 2 + color[1][i]) / 3}
+                    color[3] = (0...3).map{|i| (color[0][i] + color[1][i] * 2) / 3}
+                else
+                    color[2] = (0...3).map{|i| (color[0][i] + color[1][i]) / 2}
+                    color[3] = [0, 0, 0]
+                end
+                color.map!{|e| e.pack('C3')}
+                code = BinUtils.get_int32_le(bin, 12)
+                [color, code]
+            end
+
+            def self.decode_dxt5_alpha(bin)
+                a0 = BinUtils.get_int8(bin, 0)
+                a1 = BinUtils.get_int8(bin, 1)
+                alpha = [a0, a1, nil, nil, nil, nil, nil, nil]
+                if a0 > a1
+                    alpha[2, 6] = (1..6).map{|n| (a0 * (7-n) + a1 * n) / 7}
+                else
+                    alpha[2, 4] = (1..4).map{|n| (a0 * (5-n) + a1 * n) / 5}
+                    alpha[6] = 0
+                    alpha[7] = 255
+                end
+                alpha.pack('C8')
+                code = BinUtils.get_int64_le(bin) >> 16
+                [alpha, code]
+            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]
+            end
+
+            def self.get_rgb565a(c)
                 r = (c & 0xf800) >> 8
                 g = (c & 0x07e0) >> 3
                 b = (c & 0x001f) << 3

lib/mikunyan/decoders/image_decoder.rb

@@ -41,6 +41,8 @@ module Mikunyan
                 decode_r16(width, height, bin)
             when 10
                 decode_dxt1(width, height, bin)
+            when 12
+                decode_dxt5(width, height, bin)
             when 13
                 decode_rgba4444(width, height, bin, endian)
             when 14
@@ -353,6 +355,11 @@ module Mikunyan
             ChunkyPNG::Image.from_rgba_stream(width, height, mem).flip
         end
 
+        # Decode image from DXT1 compressed binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
         def self.decode_dxt1(width, height, bin)
             bw = (width + 3) / 4
             bh = (height + 3) / 4
@@ -366,6 +373,24 @@ module Mikunyan
             ret.crop(0, 0, height, width).flip
         end
 
+        # Decode image from DXT5 compressed binary
+        # @param [Integer] width image width
+        # @param [Integer] height image height
+        # @param [String] bin binary to decode
+        # @return [ChunkyPNG::Image] decoded image
+        def self.decode_dxt5(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_dxt5_block(bin.byteslice((bx + by * bw) * 16, 16))
+                    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