From d647261de22179edd8a734e6a6f293c61f870e1d Mon Sep 17 00:00:00 2001
From: themightyoarfish <rdiederichse@uos.de>
Date: Thu, 11 Jun 2015 14:59:57 +0200
Subject: [PATCH] Fixed alpha preservation when converting 4-channel Mat to
 UIImage

---
 modules/imgcodecs/src/ios_conversions.mm | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/modules/imgcodecs/src/ios_conversions.mm b/modules/imgcodecs/src/ios_conversions.mm
index 43268734c9..0b771f1cbc 100644
--- a/modules/imgcodecs/src/ios_conversions.mm
+++ b/modules/imgcodecs/src/ios_conversions.mm
@@ -66,6 +66,10 @@ UIImage* MatToUIImage(const cv::Mat& image) {
     CGDataProviderRef provider =
             CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
 
+    // Preserve alpha transparency, if exists
+    bool alpha = cvMat.channels() == 4;
+    CGBitmapInfo bitMapInfo = (alpha ? kCGImageAlphaLast : kCGImageAlphaNone) | kCGBitmapByteOrderDefault;
+
     // Creating CGImage from cv::Mat
     CGImageRef imageRef = CGImageCreate(image.cols,
                                         image.rows,
@@ -73,8 +77,7 @@ UIImage* MatToUIImage(const cv::Mat& image) {
                                         8 * image.elemSize(),
                                         image.step.p[0],
                                         colorSpace,
-                                        kCGImageAlphaNone|
-                                        kCGBitmapByteOrderDefault,
+                                        bitmapInfo,
                                         provider,
                                         NULL,
                                         false,