QImage ALPHA：报错

问题解决了 convertToFormat转换下格式

但是又有新问题了 转换前和转换后每一个像素里面的数据都一摸一样 为啥就显示不一样呢

bool QImageReader::read(QImage *image)
{
    if (!image) {
        qWarning("QImageReader::read: cannot read into null pointer");
        return false;
    }

    if (!d->handler && !d->initHandler())
        return false;

    // set the handler specific options.
    if (d->handler->supportsOption(QImageIOHandler::ScaledSize) && d->scaledSize.isValid()) {
        if ((d->handler->supportsOption(QImageIOHandler::ClipRect) && !d->clipRect.isNull())
            || d->clipRect.isNull()) {
            // Only enable the ScaledSize option if there is no clip rect, or
            // if the handler also supports ClipRect.
            d->handler->setOption(QImageIOHandler::ScaledSize, d->scaledSize);
        }
    }
    if (d->handler->supportsOption(QImageIOHandler::ClipRect) && !d->clipRect.isNull())
        d->handler->setOption(QImageIOHandler::ClipRect, d->clipRect);
    if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull())
        d->handler->setOption(QImageIOHandler::ScaledClipRect, d->scaledClipRect);
    if (d->handler->supportsOption(QImageIOHandler::Quality))
        d->handler->setOption(QImageIOHandler::Quality, d->quality);

    // read the image
    if (!d->handler->read(image)) {
        d->imageReaderError = InvalidDataError;
        d->errorString = QLatin1String(QT_TRANSLATE_NOOP(QImageReader, "Unable to read image data"));
        return false;
    }

    // provide default implementations for any unsupported image
    // options
    if (d->handler->supportsOption(QImageIOHandler::ClipRect) && !d->clipRect.isNull()) {
        if (d->handler->supportsOption(QImageIOHandler::ScaledSize) && d->scaledSize.isValid()) {
            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // all features are supported by the handler; nothing to do.
            } else {
                // the image is already scaled, so apply scaled clipping.
                if (!d->scaledClipRect.isNull())
                    *image = image->copy(d->scaledClipRect);
            }
        } else {
            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // supports scaled clipping but not scaling, most
                // likely a broken handler.
            } else {
                if (d->scaledSize.isValid()) {
                    *image = image->scaled(d->scaledSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
                }
                if (d->scaledClipRect.isValid()) {
                    *image = image->copy(d->scaledClipRect);
                }
            }
        }
    } else {
        if (d->handler->supportsOption(QImageIOHandler::ScaledSize) && d->scaledSize.isValid()) {
            // in this case, there's nothing we can do. if the
            // plugin supports scaled size but not ClipRect, then
            // we have to ignore ClipRect."

            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // nothing to do (ClipRect is ignored!)
            } else {
                // provide all workarounds.
                if (d->scaledClipRect.isValid()) {
                    *image = image->copy(d->scaledClipRect);
                }
            }
        } else {
            if (d->handler->supportsOption(QImageIOHandler::ScaledClipRect) && !d->scaledClipRect.isNull()) {
                // this makes no sense; a handler that supports
                // ScaledClipRect but not ScaledSize is broken, and we
                // can't work around it.
            } else {
                // provide all workarounds.
                if (d->clipRect.isValid())
                    *image = image->copy(d->clipRect);
                if (d->scaledSize.isValid())
                    *image = image->scaled(d->scaledSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
                if (d->scaledClipRect.isValid())
                    *image = image->copy(d->scaledClipRect);
            }
        }
    }

    return true;
}

找到核心代码了就是看不懂 到底怎么回事