[英]Resize JPEG image to fixed width, while keeping aspect ratio as it is
如何在保持寬高比的同時將JPEG圖像調整為固定寬度? 以一種簡單的方式,同時保持質量。
這只會在垂直軸上縮放:
public static Image ResizeImageFixedWidth(Image imgToResize, int width)
{
int sourceWidth = imgToResize.Width;
int sourceHeight = imgToResize.Height;
float nPercent = ((float)width / (float)sourceWidth);
int destWidth = (int)(sourceWidth * nPercent);
int destHeight = (int)(sourceHeight * nPercent);
Bitmap b = new Bitmap(destWidth, destHeight);
Graphics g = Graphics.FromImage((Image)b);
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(imgToResize, 0, 0, destWidth, destHeight);
g.Dispose();
return (Image)b;
}
如果要將寬度減少25%至固定值,則必須將高度減少25%。
如果要將寬度增加25%至固定值,則必須將高度增加25%。
這真的很簡單。
假設有一個( double width
)變量:
Image imgOriginal = Bitmap.FromFile(path);
double height = (imgOriginal.Height * width) / imgOriginal.Width;
Image imgnew = new Bitmap((int)width, (int)height, PixelFormat.Format32bppArgb);
Graphics g = Graphics.FromImage(imgnew);
g.DrawImage(imgOriginal, new Point[]{new Point(0,0), new Point(width, 0), new Point(0, height)}, new Rectangle(0,0,imgOriginal.Width, imgOriginal.Height), GraphicsUnit.Pixel);
最后,您將獲得一個新的寬度為xheight的圖像,然后需要刷新圖形並保存imgnew。
我認為如果您搜索它們,將會有很多示例。 這是我常用的那個...
public static Stream ResizeGdi(Stream stream, System.Drawing.Size size)
{
Image image = Image.FromStream(stream);
int width = image.Width;
int height = image.Height;
int sourceX = 0, sourceY = 0, destX = 0, destY = 0;
float percent = 0, percentWidth = 0, percentHeight = 0;
percentWidth = ((float)size.Width / (float)width);
percentHeight = ((float)size.Height / (float)height);
int destW = 0;
int destH = 0;
if (percentHeight < percentWidth)
{
percent = percentHeight;
}
else
{
percent = percentWidth;
}
destW = (int)(width * percent);
destH = (int)(height * percent);
MemoryStream mStream = new MemoryStream();
if (destW == 0
&& destH == 0)
{
image.Save(mStream, System.Drawing.Imaging.ImageFormat.Jpeg);
return mStream;
}
using (Bitmap bitmap = new Bitmap(destW, destH, System.Drawing.Imaging.PixelFormat.Format48bppRgb))
{
using (System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(bitmap))
{
//graphics.Clear(Color.Red);
graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
graphics.DrawImage(image,
new Rectangle(destX, destY, destW, destH),
new Rectangle(sourceX, sourceY, width, height),
GraphicsUnit.Pixel);
}
bitmap.Save(mStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}
mStream.Position = 0;
return mStream as Stream;
}
調用代碼示例...
Stream stream = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.None);
resizedStream = ImageUtility.ResizeGdi(stream, new System.Drawing.Size(resizeWidth, resizeHeight));
快速搜索代碼項目已找到以下文章。 它允許調整圖像的大小,該圖像接受布爾值以限制新圖像以保持原始寬高比。 我不確定畫質如何,因為沒有提供截圖。 在這里看到文章
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