refactor(image): add magic to image header (#5051)

Signed-off-by: Xu Xingliang <xuxingliang@xiaomi.com>

examples/libs/gif/lv_example_gif_1.py

@@ -11,7 +11,7 @@ fs_driver.fs_register(fs_drv, 'S')
 #
 image_bulb_gif = lv.image_dsc_t(
     {
-        "header": {"always_zero": 0, "w": 0, "h": 0,  "cf": lv.COLOR_FORMAT.RAW},
+        "header": {"w": 0, "h": 0,  "cf": lv.COLOR_FORMAT.RAW},
         "data_size": 0,
         "data": img_bulb_gif_map,
     }

examples/libs/lodepng/lv_example_lodepng_1.py

@@ -5,7 +5,7 @@ from img_wink_png import img_wink_png_map
 
 image_wink_png = lv.image_dsc_t(
     {
-        "header": {"always_zero": 0, "w": 50, "h": 50,  "cf": lv.COLOR_FORMAT.RAW_ALPHA},
+        "header": {"w": 50, "h": 50,  "cf": lv.COLOR_FORMAT.RAW_ALPHA},
         "data_size": 5158,
         "data": img_wink_png_map,
     }

scripts/LVGLImage.py

@@ -325,8 +325,8 @@ class LVGLImageHeader:
     @property
     def binary(self) -> bytearray:
         binary = bytearray()
+        binary += uint8_t(0x19)  # magic number for lvgl version 9
         binary += uint8_t(self.cf.value)
-        binary += uint8_t(0)  # 8bits format
         binary += uint16_t(self.flags)  # 16bits flags
 
         binary += uint16_t(self.w)  # 16bits width
@@ -612,6 +612,7 @@ uint8_t {varname}_map[] = {{
 }};
 
 const lv_img_dsc_t {varname} = {{
+  .header.magic = LV_IMAGE_HEADER_MAGIC,
   .header.cf = LV_COLOR_FORMAT_{self.cf.name},
   .header.flags = {flags},
   .header.w = {self.w},

src/draw/lv_image_buf.h

@@ -40,6 +40,11 @@ extern "C" {
 
 #define _LV_ZOOM_INV_UPSCALE 5
 
+/** Magic number for lvgl image, 9 means lvgl version 9
+ *  It must not be a valid ASCII character nor larger than 0x80. See `lv_image_src_get_type`.
+ */
+#define LV_IMAGE_HEADER_MAGIC (0x19)
+
 /**********************
  *      TYPEDEFS
  **********************/
@@ -89,12 +94,6 @@ typedef enum {
     LV_IMAGE_COMPRESS_LZ4,
 } lv_image_compress_t;
 
-/**
- * The first 8 bit is very important to distinguish the different source types.
- * For more info see `lv_image_get_src_type()` in lv_img.c
- * On big endian systems the order is reversed so cf and always_zero must be at
- * the end of the struct.
- */
 #if LV_BIG_ENDIAN_SYSTEM
 typedef struct {
     uint32_t reserved_2: 16;    /*Reserved to be used later*/
@@ -102,18 +101,13 @@ typedef struct {
     uint32_t h: 16;
     uint32_t w: 16;
     uint32_t flags: 16;         /*Image flags, see `lv_image_flags_t`*/
-    uint32_t reserved_1: 8;     /*Reserved by LVGL for later use*/
+    uint32_t cf : 8;            /*Color format: See `lv_color_format_t`*/
-    uint32_t always_zero : 3;   /*It the upper bits of the first byte. Always zero to look like a
+    uint32_t magic: 8;          /*Magic number. Must be LV_IMAGE_HEADER_MAGIC*/
-                                  non-printable character*/
-    uint32_t cf : 5;            /*Color format: See `lv_color_format_t`*/
 } lv_image_header_t;
 #else
 typedef struct {
-    uint32_t cf : 5;            /*Color format: See `lv_color_format_t`*/
+    uint32_t magic: 8;          /*Magic number. Must be LV_IMAGE_HEADER_MAGIC*/
-    uint32_t always_zero : 3;   /*It the upper bits of the first byte. Always zero to look like a
+    uint32_t cf : 8;            /*Color format: See `lv_color_format_t`*/
-                                  non-printable character*/
-
-    uint32_t reserved_1: 8;     /*Reserved by LVGL for later use*/
     uint32_t flags: 16;         /*Image flags, see `lv_image_flags_t`*/
 
     uint32_t w: 16;

src/libs/bin_decoder/lv_bin_decoder.c

@@ -123,6 +123,17 @@ lv_result_t lv_bin_decoder_info(lv_image_decoder_t * decoder, const void * src,
                 return LV_RESULT_INVALID;
             }
 
+            /**
+             * @todo
+             * This is a temp backward compatibility solution after adding
+             * magic in image header.
+             */
+            if(header->magic != LV_IMAGE_HEADER_MAGIC) {
+                LV_LOG_WARN("Legacy bin image detected: %s", (char *)src);
+                header->cf = header->magic;
+                header->magic = LV_IMAGE_HEADER_MAGIC;
+            }
+
             /*File is always read to buf, thus data can be modified.*/
             header->flags |= LV_IMAGE_FLAGS_MODIFIABLE;
         }