如何为 QImage 检测足够的格式（数据类型）以消耗最少的 RAM？

Question

I want use minimum RAM when i load Image in QImage in Qt, if we don't have any information about Dpi or type(RGB16 or RGBA32 or...) of image in image header.

Any idea or code or method to detect automatically image type like ( QImage::Format_RGB32 or QImage::Format_RGB16 or...) for QImage ?

Answer 1

The QImage is inheriting QPaintDevice . It's not a binary format of an image nor contains or anything else like that. Imagine it as a piece of memory with some methods and member properties that can explain the content of that memory or how you can draw pixels on that piece of memory. For example, the method QImage::load will use the QImageReader instance to load an image file like JPG, PNG, BMP, etc and initializes everything needed for QImage to hold that data. QImageReader can automatically detect image format. You will then be able to convert this QImage instance using QImage::convertToFormat method.

QImage img;
img.load("/some/path/to/sample.png");
QImage converted = img.convertToFormat(QImage::Format_RGB16);