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;
+}

src/raylib.h

@@ -1334,6 +1334,7 @@ RLAPI Image ImageCopy(Image image);
 RLAPI Image ImageFromImage(Image image, Rectangle rec);                                                  // Create an image from another image piece
 RLAPI Image ImageText(const char *text, int fontSize, Color color);                                      // Create an image from text (default font)
 RLAPI Image ImageTextEx(Font font, const char *text, float fontSize, float spacing, Color tint);         // Create an image from text (custom sprite font)
+RLAPI Image ImageMaskFromImage(Image image, Color color, float threshold);                               // Create an image mask from an image (alpha channel)
 RLAPI void ImageFormat(Image *image, int newFormat);                                                     // Convert image data to desired format
 RLAPI void ImageToPOT(Image *image, Color fill);                                                         // Convert image to POT (power-of-two)
 RLAPI void ImageCrop(Image *image, Rectangle crop);                                                      // Crop an image to a defined rectangle
@@ -1394,6 +1395,7 @@ RLAPI void ImageDrawTextEx(Image *dst, Font font, const char *text, Vector2 posi
 // NOTE: These functions require GPU access
 RLAPI Texture2D LoadTexture(const char *fileName);                                                       // Load texture from file into GPU memory (VRAM)
 RLAPI Texture2D LoadTextureFromImage(Image image);                                                       // Load texture from image data
+RLAPI Texture2D LoadTextureMaskFromImage(Image image, Color color, float threshold);                            // Load texture mask from image data (alpha channel)
 RLAPI TextureCubemap LoadTextureCubemap(Image image, int layout);                                        // Load cubemap from image, multiple image cubemap layouts supported
 RLAPI RenderTexture2D LoadRenderTexture(int width, int height);                                          // Load texture for rendering (framebuffer)
 RLAPI bool IsTextureReady(Texture2D texture);                                                            // Check if a texture is ready

src/rtextures.c

@@ -1630,6 +1630,44 @@ Image ImageTextEx(Font font, const char *text, float fontSize, float spacing, Co
     return imText;
 }
 
+Image ImageMaskFromImage(const Image image, const Color color, float threshold)
+{
+    Image mask = { 0 };
+
+    // Security check to avoid program crash
+    if ((image.data == NULL) || (image.width == 0) || (image.height == 0))
+        return mask;
+
+    // Set threshold to at least 0.0f
+    if (threshold < 0.0f) {
+        threshold = 0.0f;
+    }
+
+    Vector4 *pixels = LoadImageDataNormalized(image);
+
+    mask.format = PIXELFORMAT_UNCOMPRESSED_R8G8B8A8;
+    mask.height = image.height;
+    mask.width = image.width;
+    mask.mipmaps = 1;
+
+    Color *new_pixels = (Color *) RL_CALLOC(image.width * image.height, sizeof(Color));
+
+    for (int i = 0; i < mask.width * mask.height; i++)
+    {
+        if (pixels[i].w > threshold)
+            new_pixels[i] = color;
+        else
+            new_pixels[i] = (Color) { 0 };
+    }
+
+    mask.data = new_pixels;
+
+    RL_FREE(pixels);
+    pixels = NULL;
+
+    return mask;
+}
+
 // Resize and image to new size using Nearest-Neighbor scaling algorithm
 void ImageResizeNN(Image *image,int newWidth,int newHeight)
 {
@@ -3979,15 +4017,14 @@ Texture2D LoadTexture(const char *fileName)
 
 // Load a texture from image data
 // NOTE: image is not unloaded, it must be done manually
-Texture2D LoadTextureFromImage(Image image)
+Texture2D LoadTextureFromImage(Image image) {
-{
+  Texture2D texture = {0};
-    Texture2D texture = { 0 };
 
-    if ((image.width != 0) && (image.height != 0))
+  if ((image.width != 0) && (image.height != 0)) {
-    {
+    texture.id = rlLoadTexture(image.data, image.width, image.height,
-        texture.id = rlLoadTexture(image.data, image.width, image.height, image.format, image.mipmaps);
+                               image.format, image.mipmaps);
-    }
+  } else
-    else TRACELOG(LOG_WARNING, "IMAGE: Data is not valid to load texture");
+    TRACELOG(LOG_WARNING, "IMAGE: Data is not valid to load texture");
 
   texture.width = image.width;
   texture.height = image.height;
@@ -3997,6 +4034,14 @@ Texture2D LoadTextureFromImage(Image image)
   return texture;
 }
 
+Texture2D LoadTextureMaskFromImage(Image image, Color color, float threshold)
+{
+    const Image mask = ImageMaskFromImage(image, color, threshold);
+    const Texture result = LoadTextureFromImage(mask);
+    UnloadImage(mask);
+    return result;
+}
+
 // Load cubemap from image, multiple image cubemap layouts supported
 TextureCubemap LoadTextureCubemap(Image image, int layout)
 {