You would like to skip creating a temporary file and pass the image (not the path to the image) to ksnip and ksnip should open it up as a new image just as if you created a screenshot with knsip (the image should be shown ad not saved without a path)?

Yes, exactly!

My previous comment is also not correct, passing the path to image as single parameter works like the -f flag, not the -e flag. The -e flag is only relevant for taking screenshots currently.

Hm? Isn't the -f flag for --fullscreen? I tried using -e with any image path and it works the same way as passing the image path as a single parameter.

I think the simplest setup is to use image magick commands:

# Show magick logo using feh image viewer
magick logo: png:- | feh -

# Show a red block using feh image viewer
magick -size 128x128 xc:rgb\(255,0,0\) png:- | feh -

Thanks, we'll into it but as said, can't promise any time frame.

No problem, take your time.

Hi, I had some free time today, so I tried to deal with it a little bit (although I'm not good with C++ and Qt).
I managed to make it work at least on Linux.

I implemented it using this info as reference: https://stackoverflow.com/questions/25711302/how-to-read-stdin-to-end-in-qt/25715691#25715691

I cannot open a PR because I cannot confirm that the code is 100% correct, but I will paste the diff/patch here, so that I can help you in some way:

diff --git a/src/bootstrapper/StandAloneBootstrapper.cpp b/src/bootstrapper/StandAloneBootstrapper.cpp
index 32c9667..8bfe0e9 100644
--- a/src/bootstrapper/StandAloneBootstrapper.cpp
+++ b/src/bootstrapper/StandAloneBootstrapper.cpp
@@ -17,6 +17,7 @@
  * Boston, MA 02110-1301, USA.
  */
 
+#include <iostream>
 #include "StandAloneBootstrapper.h"
 
 StandAloneBootstrapper::StandAloneBootstrapper() :
@@ -122,7 +123,20 @@ CaptureModes StandAloneBootstrapper::getCaptureMode() const
 int StandAloneBootstrapper::startKsnipAndEditImage(const QApplication &app)
 {
 	auto pathToImage = getImagePath();
-	QPixmap pixmap(pathToImage);
+	QPixmap pixmap;
+	if (pathToImage == "-") {
+		qWarning("Reading image from stdin.");
+		QByteArray stdinImage;
+		while(!std::cin.eof()) {
+			char arr[1024];
+			std::cin.read(arr, sizeof(arr));
+			int s = std::cin.gcount();
+			stdinImage.append(arr, s);
+		}
+		pixmap.loadFromData(stdinImage);
+	} else {
+		pixmap = QPixmap(pathToImage);
+	}
 
 	if (pixmap.isNull()) {
 		qWarning("Unable to open image file %s.", qPrintable(pathToImage));

Thanks for providing this, it will definitely speed up the implementation. I'll plan it for 1.8.0.
I'll take care of adding it to the application.

This has been implemented. Thanks for providing the logic for this feature!

This works for me, but when I run ksnip as a single instance, it fails the second time.
For example:

# Opens ksnip, works as expected
 convert logo: - | ksnip -e - &
# Fails with  `Warning: Unable to open image file -.`
 convert logo: - | ksnip -e - &

When I disable running as a single instance it works as expected, however I'd loose the nice tabbed interface.

@yetifrisstlama this issue should be fixed now.