refactor rgb565

ext/decoders/native/main.c

@@ -8,9 +8,9 @@
 static VALUE rb_decode_rgb565(VALUE self, VALUE rb_data, VALUE size, VALUE big) {
     if (RSTRING_LEN(rb_data) < FIX2LONG(size) * 2)
         rb_raise(rb_eStandardError, "Data size is not enough.");
-    uint8_t *image = (uint8_t*)malloc(FIX2LONG(size) * 3);
+    uint8_t *image = (uint8_t*)malloc(FIX2LONG(size) * 4);
     decode_rgb565((uint16_t*)RSTRING_PTR(rb_data), FIX2INT(size), RTEST(big), image);
-    VALUE ret = rb_str_new((char*)image, FIX2LONG(size) * 3);
+    VALUE ret = rb_str_new((char*)image, FIX2LONG(size) * 4);
     free(image);
     return ret;
 }

ext/decoders/native/rgb.c

@@ -7,24 +7,20 @@ static inline int is_system_little() {
 
 void decode_rgb565(const uint16_t* data, const int size, const int is_big_endian, uint8_t* image) {
     const uint16_t *d = data;
-    uint8_t *p = image;
     if (is_big_endian == is_system_little()) {
-        for (int i = 0; i < size; i++, d++, p += 3) {
-            uint8_t r = *d & 0x00f8;
-            uint8_t g = (*d & 0x0007) << 5 | (*d & 0xe000) >> 11;
-            uint8_t b = (*d & 0x1f00) >> 5;
+        uint8_t *p = image;
+        for (int i = 0; i < size; i++, d++, p += 4) {
+            uint_fast8_t r = *d & 0x00f8;
+            uint_fast8_t g = (*d & 0x0007) << 5 | (*d & 0xe000) >> 11;
+            uint_fast8_t b = (*d & 0x1f00) >> 5;
             p[0] = r | r >> 5;
             p[1] = g | g >> 6;
             p[2] = b | b >> 5;
+            p[3] = 255;
         }
     } else {
-        for (int i = 0; i < size; i++, d++, p += 3) {
-            uint8_t r = (*d & 0xf800) >> 8;
-            uint8_t g = (*d & 0x07e0) >> 3;
-            uint8_t b = (*d & 0x001f) << 3;
-            p[0] = r | r >> 5;
-            p[1] = g | g >> 6;
-            p[2] = b | b >> 5;
-        }
+        uint32_t *p = (uint32_t*)image;
+        for (int i = 0; i < size; i++, d++, p++)
+            *p = (*d & 0xf800) >> 8 | *d >> 13 | (*d & 0x7e0) << 5 | (*d & 0x60) << 3 | *d << 19 | (*d & 0x1c) << 14 | 0xff000000;
     }
 }

lib/mikunyan/decoders/image_decoder.rb

@@ -126,7 +126,7 @@ module Mikunyan
         # @param [Symbol] endian endianness of binary
         # @return [ChunkyPNG::Image] decoded image
         def self.decode_rgb565(width, height, bin, endian = :big)
-            ChunkyPNG::Image.from_rgb_stream(width, height, DecodeHelper.decode_rgb565(bin, width * height, endian == :big)).flip
+            ChunkyPNG::Image.from_rgba_stream(width, height, DecodeHelper.decode_rgb565(bin, width * height, endian == :big)).flip
         end
 
         # Decode image from A8 binary