Add Images::Read method.

ui/image/image_prepare.cpp

@@ -13,6 +13,10 @@
 #include "styles/palette.h"
 #include "styles/style_basic.h"
 
+#include <QtCore/QFile>
+#include <QtCore/QBuffer>
+#include <QtGui/QImageReader>
+
 namespace Images {
 namespace {
 
@@ -111,6 +115,50 @@ std::array<QImage, 4> PrepareCorners(
 	return result;
 }
 
+ReadResult Read(ReadArgs &&args) {
+	if (args.content.isEmpty()) {
+		auto file = QFile(args.path);
+		if (file.size() > kReadBytesLimit
+			|| !file.open(QIODevice::ReadOnly)) {
+			return {};
+		}
+		args.content = file.readAll();
+	}
+	if (args.content.isEmpty()) {
+		return {};
+	}
+	auto result = ReadResult();
+	{
+		auto buffer = QBuffer(&args.content);
+		auto reader = QImageReader(&buffer);
+		reader.setAutoTransform(true);
+		if (!reader.canRead()) {
+			return {};
+		}
+		const auto size = reader.size();
+		if (size.width() * size.height() > kReadMaxArea) {
+			return {};
+		}
+		if (!reader.read(&result.image) || result.image.isNull()) {
+			return {};
+		}
+		result.animated = reader.supportsAnimation()
+			&& (reader.imageCount() > 1);
+		result.format = reader.format().toLower();
+	}
+	if (args.returnContent) {
+		result.content = args.content;
+	} else {
+		args.content = QByteArray();
+	}
+	if (args.forceOpaque
+		&& result.format != qstr("jpg")
+		&& result.format != qstr("jpeg")) {
+		result.image = prepareOpaque(std::move(result.image));
+	}
+	return result;
+}
+
 QImage prepareBlur(QImage img) {
 	if (img.isNull()) {
 		return img;

ui/image/image_prepare.h

@@ -39,6 +39,26 @@ namespace Images {
 	int radius,
 	const style::color &color);
 
+
+// Try to read images up to 64MB.
+inline constexpr auto kReadBytesLimit = 64 * 1024 * 1024;
+inline constexpr auto kReadMaxArea = 12'032 * 9'024;
+
+struct ReadArgs {
+	QString path;
+	QByteArray content;
+	QSize maxSize;
+	bool forceOpaque = false;
+	bool returnContent = false;
+};
+struct ReadResult {
+	QImage image;
+	QByteArray content;
+	QByteArray format;
+	bool animated = false;
+};
+[[nodiscard]] ReadResult Read(ReadArgs &&args);
+
 QImage prepareBlur(QImage image);
 void prepareRound(
 	QImage &image,