libgfx: draw: Add gfx_get_pix() function

Introduce gfx routine to grab the RGB value of a specific pixel at a
specific location on the screen.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 29 insertions, 0 deletions

diff --git a/lib/libgfx/include/libgfx/draw.h b/lib/libgfx/include/libgfx/draw.h
index 9f56f6c..96fe35a 100644
--- a/lib/libgfx/include/libgfx/draw.h
+++ b/lib/libgfx/include/libgfx/draw.h
@@ -103,6 +103,7 @@ struct gfx_point {
 
 int gfx_draw_shape(struct gfx_ctx *ctx, const struct gfx_shape *shape);
 int gfx_plot_point(struct gfx_ctx *ctx, const struct gfx_point *point);
+color_t gfx_get_pix(struct gfx_ctx *ctx, uint32_t x, uint32_t y);
 
 __always_inline static inline size_t
 gfx_io_index(struct gfx_ctx *ctx, scrpos_t x, scrpos_t y)
diff --git a/lib/libgfx/src/draw.c b/lib/libgfx/src/draw.c
index 9ef8630..784110a 100644
--- a/lib/libgfx/src/draw.c
+++ b/lib/libgfx/src/draw.c
@@ -129,6 +129,34 @@ gfx_plot_point(struct gfx_ctx *ctx, const struct gfx_point *point)
 }
 
 /*
+ * Grab the RGB value of a single pixel on
+ * the scren.
+ *
+ * @ctx: Graphics context pointer
+ * @x: X position to sample
+ * @y: Y position to sample
+ */
+color_t
+gfx_get_pix(struct gfx_ctx *ctx, uint32_t x, uint32_t y)
+{
+    const color_t ERROR_COLOR = GFX_BLACK;
+    uint32_t index;
+
+    /* The 'ctx' argument is required */
+    if (ctx == NULL) {
+        return ERROR_COLOR;
+    }
+
+    /* Are we within bounds of the screen */
+    if (gfx_pixel_bounds(ctx, x, y) < 0) {
+        return ERROR_COLOR;
+    }
+
+    index = gfx_io_index(ctx, x, y);
+    return ctx->io[index];
+}
+
+/*
  * Draw a shape onto the screen
  *
  * @ctx: libgfx graphics context