qml qt grabToImage get image bytes

Question

For some reason, saving a png back out from qml directly doesn't work. I have a qml UI on top of a Golang application. When I do

source.grabToImage(function(result){
    console.log("image: ", result.url)
if (!result.saveToFile(urlNoProtocol)){
    console.error('Unknown error saving to',urlNoProtocol);
} else {
    console.log("saved to " + urlNoProtocol)
}

I get an error saving out. The location to save the file is coming from a fileDialog and I preprocess it to remove the file:// which I understand needs to be removed before using saveToFile. However I get an unknown error saving from the above code.

I suspect this is something to do with the qml being embedded in the binary application (perhaps to do with qrc:// or something)

Anyway my current plan is to send the image to the golang backend and save it out from there, so my question is, how from grabToImage or saveToFile can I get the image bytes that I will then save?

N.B Using therecipe/qt for the interface between Golang and qml

teh_raab teh_raab · Accepted Answer · 2019-01-11T16:52:50

I have used this method for grabbing screen shots..

function performScreenShot(item, name) {
    if(typeof(item) === "undefined") {
        return;
    }
    else if(typeof(name) !== "string") {
        name = "screenshot.png"
    }

    item.grabToImage(function(result) {
        result.saveToFile(name);
    });
}

Usage example:-

performScreenShot(main, "screenshot-" + screenShotIndex + ".png")

Where main is my object id and screenShotIndex is something im incrementing so as not to override any previous capture.

Ensure that you have write permission on the device.

qml qt grabToImage get image bytes

1 Answers