<![CDATA[QImage from JSON double encoded data]]>Hi,

I'm receiving an image through JSON.

I cannot share file data due char limitation. Please download it on WeTransfer:

https://we.tl/t-Z3tgCT7NSK

It seems that the image has been double encoded: "Windows-1252" -> "UTF-8" -> "base64".

How do I revert the double encoding?

QFile qFile("image.json");
if (qFile.open(QIODeviceBase::ReadOnly))
{
	QTextStream qStream(&qFile);
	QByteArray qBuffer = qStream.readAll().toUtf8();
	QJsonParseError* pqError = nullptr;
	QJsonDocument qJsonDoc = QJsonDocument::fromJson(qBuffer, pqError);
	if (!qJsonDoc.isNull())
	{
		QJsonObject qJsonObject = qJsonDoc.object();
		if (qJsonObject.contains("IMG"))
		{
                    QString base64 = qJsonObject.value("IMG").toString();

                    //Here I need to do the double decoding
                    QImage qImage;
		}
	}
}

Regards,

]]>https://forum.qt.io/topic/164450/qimage-from-json-double-encoded-dataRSS for NodeSat, 18 Apr 2026 19:19:37 GMTWed, 18 Mar 2026 17:38:40 GMT60<![CDATA[Reply to QImage from JSON double encoded data on Thu, 19 Mar 2026 15:12:32 GMT]]>Hi,

Finally I found a solution. It seems that the error starts with the data extracted from a Database that is bad encoded. The solution:

QString qImgB64 = qJsonObject.value("IMG").toString();

// Base64 → "corrupted bytes"
QByteArray qDecoded = QByteArray::fromBase64(qImgB64.toLatin1());

// UTF-8
QString utf8Text = QStringDecoder(QStringDecoder::Utf8)(qDecoded);

// Convert to CP1252
QStringEncoder encoder(QStringEncoder::System); // or Windows-1252 "QStringEncoder encoder("Windows-1252");"
QByteArray qJpeg = encoder(utf8Text);

// Load into image
QImage qImage;
bool ok = qImage.loadFromData(qJpeg);

Thanks

]]>https://forum.qt.io/post/837192https://forum.qt.io/post/837192Thu, 19 Mar 2026 15:12:32 GMT<![CDATA[Reply to QImage from JSON double encoded data on Wed, 18 Mar 2026 19:39:09 GMT]]>Hi,

I haven't used that class yet but I think you are looking for QStringDecoder.

Hope it helps

]]>https://forum.qt.io/post/837168https://forum.qt.io/post/837168Wed, 18 Mar 2026 19:39:09 GMT