GUAC-236: Implement WebP decoding.

src/guacenc/webp.c

@@ -21,14 +21,57 @@
  */
 
 #include "config.h"
+#include "log.h"
 #include "webp.h"
 
 #include <cairo/cairo.h>
+#include <guacamole/client.h>
+#include <webp/decode.h>
 
+#include <stdint.h>
 #include <stdlib.h>
 
 cairo_surface_t* guacenc_webp_decoder(unsigned char* data, int length) {
-    /* STUB */
+
-    return NULL;
+    int width, height;
+
+    /* Validate WebP and pull dimensions */
+    if (!WebPGetInfo((uint8_t*) data, length, &width, &height)) {
+        guacenc_log(GUAC_LOG_WARNING, "Invalid WebP data");
+        return NULL;
+    }
+
+    /* Create blank Cairo surface */
+    cairo_surface_t* surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,
+            width, height);
+
+    /* Fill surface with opaque black */
+    cairo_t* cairo = cairo_create(surface);
+    cairo_set_operator(cairo, CAIRO_OPERATOR_SOURCE);
+    cairo_set_source_rgba(cairo, 0.0, 0.0, 0.0, 1.0);
+    cairo_paint(cairo);
+    cairo_destroy(cairo);
+
+    /* Finish any pending draws */
+    cairo_surface_flush(surface);
+
+    /* Pull underlying buffer and its stride */
+    int stride = cairo_image_surface_get_stride(surface);
+    unsigned char* image = cairo_image_surface_get_data(surface);
+
+    /* Read WebP into surface */
+    uint8_t* result = WebPDecodeBGRAInto((uint8_t*) data, length,
+            (uint8_t*) image, stride * height, stride);
+
+    /* Verify WebP was successfully decoded */
+    if (result == NULL) {
+        guacenc_log(GUAC_LOG_WARNING, "Invalid WebP data");
+        cairo_surface_destroy(surface);
+        return NULL;
+    }
+
+    /* WebP was read successfully */
+    return surface;
+
 }