我想裁剪并调整图像大小。这是我的代码:
Image image = Image.FromFile(AppDomain.CurrentDomain.BaseDirectory + "Cropper/tests/castle.jpg");
// Crop and resize the image.
Rectangle destination = new Rectangle(0, 0, 200, 120);
Graphics graphic = Graphics.FromImage(image);
graphic.DrawImage(image, destination, int.Parse(X1.Value), int.Parse(Y1.Value), int.Parse(Width.Value), int.Parse(Height.Value), GraphicsUnit.Pixel);
现在我假设我生成的裁剪/调整大小的图像存储在图形对象中。问题是 - 如何将其保存到文件中?
从Graphics
获得的Graphics.FromImage
对象是图像的绘图表面。因此,您可以在完成后保存图像对象。
string fileName = AppDomain.CurrentDomain.BaseDirectory + "Cropper/tests/castle.jpg");
using (Image image = Image.FromFile(fileName)
{
using (Graphics graphic = Graphics.FromImage(image))
{
// Crop and resize the image.
Rectangle destination = new Rectangle(0, 0, 200, 120);
graphic.DrawImage(image, destination, int.Parse(X1.Value), int.Parse(Y1.Value), int.Parse(Width.Value), int.Parse(Height.Value), GraphicsUnit.Pixel);
}
image.Save(fileName);
}
请注意,尽管在jpg图像上重复这样做可能不是一件好事;每次重新编码图像,由于jpg使用破坏性压缩方法,每次都会丢失一些图像质量。如果这是一次一次的图像操作,我不担心。
不,Graphics
对象不包含任何图像数据,它用于在画布上绘制,通常是屏幕或Bitmap
对象。
因此,您需要创建一个具有正确尺寸的Bitmap
对象来绘制,并为该位图创建Graphics
对象。然后你可以保存它。请记住,应该处理实现IDisposable
的对象,例如使用using
子句:
using (Image image = Image.FromFile(AppDomain.CurrentDomain.BaseDirectory + "Cropper/tests/castle.jpg")) {
// Create bitmap
using (Bitmap newImage = new Bitmap(200, 120)) {
// Crop and resize the image.
Rectangle destination = new Rectangle(0, 0, 200, 120);
using (Graphics graphic = Graphics.FromImage(newImage)) {
graphic.DrawImage(image, destination, int.Parse(X1.Value), int.Parse(Y1.Value), int.Parse(Width.Value), int.Parse(Height.Value), GraphicsUnit.Pixel);
}
newImage.Save(AppDomain.CurrentDomain.BaseDirectory + "Cropper/tests/castle_icon.jpg", ImageFormat.Jpeg);
}
}
这不是OP问题的直接答案,但它是一个经常被忽视的工具,可以让你以不同的方式处理事情,如果证明是必要的话。
人们常说,不可能获得Graphics对象的内容。这根本不是真的。使用正确的方法,您可以使用HDC和BitBlt访问画布上的数据。以下是使用C#执行此操作的一种方法:
enum TernaryRasterOperations : uint
{
/// <summary>dest = source</summary>
SRCCOPY = 0x00CC0020,
/// <summary>dest = source OR dest</summary>
SRCPAINT = 0x00EE0086,
/// <summary>dest = source AND dest</summary>
SRCAND = 0x008800C6,
/// <summary>dest = source XOR dest</summary>
SRCINVERT = 0x00660046,
/// <summary>dest = source AND (NOT dest)</summary>
SRCERASE = 0x00440328,
/// <summary>dest = (NOT source)</summary>
NOTSRCCOPY = 0x00330008,
/// <summary>dest = (NOT src) AND (NOT dest)</summary>
NOTSRCERASE = 0x001100A6,
/// <summary>dest = (source AND pattern)</summary>
MERGECOPY = 0x00C000CA,
/// <summary>dest = (NOT source) OR dest</summary>
MERGEPAINT = 0x00BB0226,
/// <summary>dest = pattern</summary>
PATCOPY = 0x00F00021,
/// <summary>dest = DPSnoo</summary>
PATPAINT = 0x00FB0A09,
/// <summary>dest = pattern XOR dest</summary>
PATINVERT = 0x005A0049,
/// <summary>dest = (NOT dest)</summary>
DSTINVERT = 0x00550009,
/// <summary>dest = BLACK</summary>
BLACKNESS = 0x00000042,
/// <summary>dest = WHITE</summary>
WHITENESS = 0x00FF0062,
/// <summary>
/// Capture window as seen on screen. This includes layered windows
/// such as WPF windows with AllowsTransparency="true"
/// </summary>
CAPTUREBLT = 0x40000000
}
[DllImport("gdi32.dll", EntryPoint = "BitBlt", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool BitBlt([In] IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, [In] IntPtr hdcSrc, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);
public static Bitmap CopyGraphicsContent(Graphics source, Rectangle rect)
{
Bitmap bmp = new Bitmap(rect.Width, rect.Height);
using (Graphics dest = Graphics.FromImage(bmp))
{
IntPtr hdcSource = source.GetHdc();
IntPtr hdcDest = dest.GetHdc();
BitBlt(hdcDest, 0, 0, rect.Width, rect.Height, hdcSource, rect.X, rect.Y, TernaryRasterOperations.SRCCOPY);
source.ReleaseHdc(hdcSource);
dest.ReleaseHdc(hdcDest);
}
return bmp;
}