created ImageMaskFromImage and LoadTextureMaskFromImage

These functions adds the possibility to retrieve a mask from the alpha
channel of an image.

examples/textures/textures_image_mask.c

@@ -0,0 +1,68 @@
+/*******************************************************************************************
+*
+*   raylib [textures] example - Retrive image mask from alpha values
+*
+*   NOTE: Images are loaded in CPU memory (RAM); textures are loaded in GPU memory (VRAM)
+*
+*   Example originally created with raylib 5.1-dev, last time updated with raylib 5.1-dev
+*
+*   Example contributed by Bruno Cabral (github.com/brccabral) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2024-2024 Bruno Cabral (github.com/brccabral) and Ramon Santamaria (@raysan5)
+*
+********************************************************************************************/
+
+#include <raylib.h>
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 612;
+
+    InitWindow(screenWidth, screenHeight, "raylib [shapes] example - draw rectangle rounded");
+
+    Image fudesumi_image = LoadImage("resources/fudesumi.png");
+    Texture2D fudesumi_texture = LoadTextureFromImage(fudesumi_image);
+    Texture2D fudesumi_mask = LoadTextureMaskFromImage(fudesumi_image, RED, 0.0f);
+
+    Image background_image = GenImageChecked(screenWidth, screenHeight, screenWidth/20, screenHeight/20, BLUE, SKYBLUE);
+    Texture2D background_texture = LoadTextureFromImage(background_image);
+
+    SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            DrawTexture(background_texture, 0, 0, WHITE);
+            DrawTexture(fudesumi_texture, 50, 50, WHITE);
+            DrawTexture(fudesumi_mask, 410, 50, WHITE);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    UnloadImage(fudesumi_image);
+    UnloadImage(background_image);
+    UnloadTexture(fudesumi_texture);
+    UnloadTexture(fudesumi_mask);
+    UnloadTexture(background_texture);
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}