在 ListView 的网格中显示 128x128 像素或更大的缩略图图标 [英] Displaying thumbnail icons 128x128 pixels or larger in a grid in ListView

问题描述

原始问题(请参阅下面的更新)

我有一个 WinForms 程序，它需要一个带有大图标(实际上是 128x128 或更大的缩略图)的可滚动图标控件，可以单击以突出显示或双击以执行某些操作.最好尽量减少浪费的空间(每个图标下方可能需要简短的文件名标题；如果文件名太长，我可以添加省略号).

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(来源:updike.org)}

顺便说一下，为了保持缩略图的适当纵横比，我必须制作自己的 128x128 位图，清除背景以匹配控件，并将这些图像居中:

public void CenterDrawImage(Bitmap target, Color background, Bitmap centerme){图形 g = Graphics.FromImage(target);g.清除(背景)；int x = (target.Width - centerme.Width)/2;int y = (target.Height - centerme.Height)/2;g.DrawImage(centerme, x, y);g.Dispose();}

解决方案

更新:

1. 设置图像列表颜色深度和图像大小(ilist.ColorDepth = ColorDepth.Depth24Bit)
2. WinForms ListView 无法更改图标间距，但可以使用 Win32 轻松完成.您需要将 LVM_SETICONSPACING 发送到您的 ListView (.net 中如何使用SendMessage win32 函数的教程很多，所以我觉得这个方向对你来说应该足够了).

Original Question (see Update below)

I have a WinForms program that needs a decent scrollable icon control with large icons (128x128 or larger thumbnails, really) that can be clicked to hilight or double clicked to perform some action. Preferably there would be minimal wasted space (short filename captions might be needed below each icon; if the filename is too long I can add an ellipsis).

_{(source: updike.org)}

I tried using a ListView with LargeIcon (default .View) and the results are disappointing:

_{(source: updike.org)}

Perhaps I am populating the control incorrectly? Code:

        ImageList ilist = new ImageList();
        this.listView.LargeImageList = ilist;
        int i = 0;
        foreach (GradorCacheFile gcf in gc.files)
        {
            Bitmap b = gcf.image128;
            ilist.Images.Add(b);
            ListViewItem lvi = new ListViewItem("text");
            lvi.ImageIndex = i;
            this.listView.Items.Add(lvi);
            i++;
        }

I need large icons with little empty space, not large empty space with embarrassingly small icons.

1. Is there a .NET control that does what I need?
   • Is there a favorite third party control that does this?
   • If not, which control would be best to inherit and tweak to make it work?
   • Should I break down and make a custom Control (which I have plenty of experience with... just don't want to go to that extreme since that is somewhat involved).

I found this tutorial about OwnerDraw but work from that basically amounts to number 3 or 4 above since that demo just shows how to spice up the rows in the details view.

Update

Adding the line

ilist.ImageSize = new Size(128, 128);

before the for loop fixed the size problem but now the images are palette-ized to 8-bit (looks like system colors?) even though the debugger shows that the images are inserted into the ImageList as 24bpp System.Drawing.Bitmap's:

_{(source: updike.org)}

1. How do I (can I?) make the images show in full 24 bit color?
   • The spacing around the icons is still rather wasteful... how do I fix that? Can I?

Update 2

Along with adding the line

ilist.ColorDepth = ColorDepth.Depth24Bit;

next after setting ilist.ImageSize, I followed arbiter's advice and changed the spacing:

[DllImport("user32.dll")]
public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

public int MakeLong(short lowPart, short highPart)
{
    return (int)(((ushort)lowPart) | (uint)(highPart << 16));
}

public void ListView_SetSpacing(ListView listview, short cx, short cy)
{
    const int LVM_FIRST = 0x1000;
    const int LVM_SETICONSPACING = LVM_FIRST + 53;
    // http://msdn.microsoft.com/en-us/library/bb761176(VS.85).aspx
    // minimum spacing = 4
    SendMessage(listview.Handle, LVM_SETICONSPACING,
    IntPtr.Zero, (IntPtr)MakeLong(cx, cy));

    // http://msdn.microsoft.com/en-us/library/bb775085(VS.85).aspx
    // DOESN'T WORK!
    // can't find ListView_SetIconSpacing in dll comctl32.dll
    //ListView_SetIconSpacing(listView.Handle, 5, 5);
}

///////////////////////////////////////////////////////////

ListView_SetSpacing(this.listView, 128 + 12, 128 + 4 + 20);

The ListView control may not be perfect or have the defaults I'd expect (like a Spacing property) but I'm glad I could tame it, in the end:

_{(source: updike.org)}

By the way, to maintain the proper aspect ratio for the thumbnails, I had to make my own 128x128 bitmaps, clear the background to match the control, and center those images:

public void CenterDrawImage(Bitmap target, Color background, Bitmap centerme)
{
    Graphics g = Graphics.FromImage(target);
    g.Clear(background);
    int x = (target.Width - centerme.Width) / 2;
    int y = (target.Height - centerme.Height) / 2;
    g.DrawImage(centerme, x, y);
    g.Dispose();
}

解决方案

For update:

1. Set image list color depth in addition to image size (ilist.ColorDepth = ColorDepth.Depth24Bit)
2. WinForms ListView does not have possibility to change icon spacing, however it can be easily done using Win32. You need to send LVM_SETICONSPACING to your ListView (there is a lot of tutorials how to use SendMessage win32 function in .net, so I think this direction must be enough for you).

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