保存图像文件和节省内存的最佳方法

Question

在我的程序中,我正在创建一些大图片(Image对象),并将它们保存到磁盘.然后我将它们添加到一个列表中List<Image>但是在保存了50张图片并将它们作为Image对象添加到我的文件后,imageList它会占用内存的loooooot.我尝试在50个图像上执行此操作,只保存纯图像对象,我的程序在进程管理器中上升到160 MB.所以我必须找到一种方法来保存图片并将它们添加到列表中,而不会占用所有内存.

所以我有几个解决方案,我很想听听你对它们的看法,或者你有更好的解决方案.

1. 压缩byte[]图像对象的数组.
2. 压缩memorysteam对象的流.
3. 将byte[]图像对象的数组转换为字符串,然后压缩字符串.

我在c#中这样做.

Answer 1

不要使用.Net DeflateStream等压缩图像(因为在所有情况下都存在实际增加数据大小的已知问题) - 将其直接保存为类似.png的内容.

Bitmap bmp;
// ...
bmp.Save("foo.png", System.Drawing.Imaging.ImageFormat.Png);

确保丢弃您创建的图像(保存后).

您无法在内存中压缩图像 - 因为Windows GDI(.Net使用)需要图像,实际上是未压缩的位图形式(因此当您加载压缩图像时,它将被解压缩).

你应该看看按需加载它们.这是一个类似于ImageList你可能会觉得有用的类:

public class DelayedImagedList : Component
{
    // Item1 = Dispose for the image.
    // Item2 = At creation: the method to load the image. After loading: the method to return the image.
    // Item3 = The original filename.
    private List<Tuple<Action, Func<Image>, string>> _images = new List<Tuple<Action,Func<Image>,string>>();
    private Dictionary<string, int> _imageKeyMap = new Dictionary<string, int>();

    // Access images.
    public Image this[string key] { get { return _images[_imageKeyMap[key]].Item2(); } }
    public Image this[int index] { get { return _images[index].Item2(); } }
    public int Count { get { return _images.Count; } }

    // Use this to add an image according to its filename.
    public void AddImage(string key, string filename) { _imageKeyMap.Add(key, AddImage(filename)); }
    public int AddImage(string filename)
    {
        var index = _images.Count;
        _images.Add(Tuple.Create<Action, Func<Image>, string>(
            () => {}, // Dispose
            () => // Load image.
            {
                var result = Image.FromFile(filename);
                // Replace the method to load the image with one to simply return it.
                _images[index] = Tuple.Create<Action, Func<Image>, string>(
                    result.Dispose, // We need to dispose it now.
                    () => result, // Just return the image.
                    filename);
                return result;
            }, 
            filename));
        return index;
    }

    // This will unload an image from memory.
    public void Reset(string key) { Reset(_imageKeyMap[key]); }
    public void Reset(int index)
    {
        _images[index].Item1(); // Dispose the old value.
        var filename = _images[index].Item3;

        _images[index] = Tuple.Create<Action, Func<Image>, string>(
            () => { }, 
            () =>
            {
                var result = Image.FromFile(filename);
                _images[index] = Tuple.Create<Action, Func<Image>, string>(
                    result.Dispose, 
                    () => result, 
                    filename);
                return result;
            }, 
            filename);
    }

    // These methods are available on ImageList.
    public void Draw(Graphics g, Point pt, int index) { g.DrawImage(this[index], pt); }
    public void Draw(Graphics g, int x, int y, int index) { g.DrawImage(this[index], x, y); }
    public void Draw(Graphics g, int x, int y, int width, int height, int index) { g.DrawImage(this[index], x, y, width, height); }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            foreach (var val in _images) { val.Item1(); }
            _images.Clear();
            _imageKeyMap.Clear();
        }
        base.Dispose(disposing);
    }
}