refactor: minor refactoring and widget docs update

examples/widgets/image/lv_example_image_4.c

@@ -0,0 +1,41 @@
+#include "../../lv_examples.h"
+#if LV_USE_IMG && LV_BUILD_EXAMPLES
+
+static void ofs_y_anim(void * img, int32_t v)
+{
+    lv_image_set_offset_y(img, v);
+}
+
+/**
+ * Image styling and offset
+ */
+void lv_example_image_4(void)
+{
+    LV_IMAGE_DECLARE(img_skew_strip);
+
+    static lv_style_t style;
+    lv_style_init(&style);
+    lv_style_set_bg_color(&style, lv_palette_main(LV_PALETTE_YELLOW));
+    lv_style_set_bg_opa(&style, LV_OPA_COVER);
+    lv_style_set_image_recolor_opa(&style, LV_OPA_COVER);
+    lv_style_set_image_recolor(&style, lv_color_black());
+
+    lv_obj_t * img = lv_image_create(lv_screen_active());
+    lv_obj_add_style(img, &style, 0);
+    lv_image_set_src(img, &img_skew_strip);
+    lv_obj_set_size(img, 150, 100);
+    lv_obj_center(img);
+
+    lv_anim_t a;
+    lv_anim_init(&a);
+    lv_anim_set_var(&a, img);
+    lv_anim_set_exec_cb(&a, ofs_y_anim);
+    lv_anim_set_values(&a, 0, 100);
+    lv_anim_set_duration(&a, 3000);
+    lv_anim_set_playback_time(&a, 500);
+    lv_anim_set_repeat_count(&a, LV_ANIM_REPEAT_INFINITE);
+    lv_anim_start(&a);
+
+}
+
+#endif