Added possibility to determine the image type in Media::Android::decodeImage()

Summary: The Android NDK does not provide this kind of information, so that we need to determine the type based on the buffer's magic number.

Reviewed By: enpe

Differential Revision:
D79398813

Privacy Context Container: L1192943

fbshipit-source-id: 0e3afb75d063dac4a72255e68073866baa151a7c

Author: janherlingmeta

impl/ocean/media/android/Image.cpp

@@ -28,7 +28,7 @@ namespace Android
 
 #if defined(__ANDROID_API__) && __ANDROID_API__ >= 30
 
-Frame Image::decodeImage(const void* buffer, const size_t size, const std::string& imageBufferTypeIn, std::string* imageBufferTypeOut)
+Frame Image::decodeImage(const void* buffer, const size_t size, const std::string& /*imageBufferTypeIn*/, std::string* imageBufferTypeOut)
 {
 	ocean_assert(buffer != nullptr && size != 0);
 
@@ -40,7 +40,14 @@ Frame Image::decodeImage(const void* buffer, const size_t size, const std::strin
 	ScopedAImageDecoder aImageDecoder;
 	if (AImageDecoder_createFromBuffer(buffer, size, &aImageDecoder.resetObject()) == ANDROID_IMAGE_DECODER_SUCCESS)
 	{
-		return decodeImage(*aImageDecoder);
+		Frame result = decodeImage(*aImageDecoder);
+
+		if (result.isValid() && imageBufferTypeOut != nullptr)
+		{
+			*imageBufferTypeOut = determineImageType(buffer, size);
+		}
+
+		return result;
 	}
 
 	return Frame();
@@ -86,6 +93,41 @@ Frame Image::readImage(const std::string& filename)
 	return Frame();
 }
 
+std::string Image::determineImageType(const void* buffer, const size_t size)
+{
+	ocean_assert(buffer != nullptr && size != 0);
+
+	const uint8_t* data = (const uint8_t*)(buffer);
+
+	if (size >= 4)
+	{
+		if (data[0] == 0x89 && data[1] == 0x50 && data[2] == 0x4E && data[3] == 0x47)
+		{
+			return "png";
+		}
+
+		if (data[0] == 0x47 && data[1] == 0x49 && data[2] == 0x46 && data[3] == 0x38)
+		{
+			return "gif";
+		}
+	}
+
+	if (size >= 2)
+	{
+		if (data[0] == 0xFF && data[1] == 0xD8)
+		{
+			return "jpg";
+		}
+
+		if (data[0] == 0x42 && data[1] == 0x4D)
+		{
+			return "bmp";
+		}
+	}
+
+	return std::string();
+}
+
 #if defined(__ANDROID_API__) && __ANDROID_API__ >= 30
 
 Frame Image::decodeImage(AImageDecoder* aImageDecoder)

impl/ocean/media/android/Image.h

@@ -73,6 +73,14 @@ class Image
 
 	protected:
 
+		/**
+		 * Returns the image type of a given buffer.
+		 * @param buffer The buffer from which the image type will be determined, must be valid
+		 * @param size The size of the given buffer in bytes, with range [1, infinity)
+		 * @return The image type, an empty string if the type could not be determined, e.g., "jpg", "png", "bmp", "tiff", etc.
+		 */
+		static std::string determineImageType(const void* buffer, const size_t size);
+
 #if defined(__ANDROID_API__) && __ANDROID_API__ >= 30
 
 		/**