feat(libs): add libpng decoder (#4569)

Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com>
Co-authored-by: pengyiqiang <pengyiqiang@xiaomi.com>
Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

examples/libs/libpng/index.rst

@@ -0,0 +1,6 @@
+Open a PNG image from file
+--------------------------
+
+.. lv_example:: libs/libpng/lv_example_libpng_1
+  :language: c
+

examples/libs/libpng/lv_example_libpng.h

@@ -0,0 +1,38 @@
+/**
+ * @file lv_example_libpng.h
+ *
+ */
+
+#ifndef LV_EXAMPLE_LIBPNG_H
+#define LV_EXAMPLE_LIBPNG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*********************
+ *      INCLUDES
+ *********************/
+
+/*********************
+ *      DEFINES
+ *********************/
+
+/**********************
+ *      TYPEDEFS
+ **********************/
+
+/**********************
+ * GLOBAL PROTOTYPES
+ **********************/
+void lv_example_libpng_1(void);
+
+/**********************
+ *      MACROS
+ **********************/
+
+#ifdef __cplusplus
+} /*extern "C"*/
+#endif
+
+#endif /*LV_EXAMPLE_LIBPNG_H*/

examples/libs/libpng/lv_example_libpng_1.c

@@ -0,0 +1,31 @@
+#include "../../lv_examples.h"
+#if LV_BUILD_EXAMPLES
+
+#if LV_USE_LIBPNG
+
+/**
+ * Open a PNG image from a file
+ */
+void lv_example_libpng_1(void)
+{
+    lv_obj_t * img;
+
+    img = lv_image_create(lv_scr_act());
+    /* Assuming a File system is attached to letter 'A'
+     * E.g. set LV_USE_FS_STDIO 'A' in lv_conf.h */
+    lv_image_set_src(img, "A:lvgl/examples/libs/libpng/png_demo.png");
+    lv_obj_center(img);
+}
+
+#else
+
+void lv_example_libpng_1(void)
+{
+    lv_obj_t * label = lv_label_create(lv_scr_act());
+    lv_label_set_text(label, "LibPNG is not installed");
+    lv_obj_center(label);
+}
+
+#endif
+
+#endif

examples/libs/libpng/lv_example_libpng_1.py

@@ -0,0 +1,11 @@
+#!/opt/bin/lv_micropython -i
+import lvgl as lv
+import display_driver
+import fs_driver
+
+fs_drv = lv.fs_drv_t()
+fs_driver.fs_register(fs_drv, 'S')
+
+image = lv.image(lv.scr_act())
+image.set_src("S:png_demo.png")
+image.center()

examples/libs/lv_example_libs.h

@@ -19,6 +19,7 @@ extern "C" {
 #include "freetype/lv_example_freetype.h"
 #include "gif/lv_example_gif.h"
 #include "lodepng/lv_example_lodepng.h"
+#include "libpng/lv_example_libpng.h"
 #include "qrcode/lv_example_qrcode.h"
 #include "rlottie/lv_example_rlottie.h"
 #include "tjpgd/lv_example_tjpgd.h"