如何压缩图像之前存储在asp.net中
本文关键字：存储 asp net 图像 何压缩 压缩 | 更新日期: 2023-09-27 18:03:54
这是我的add image代码。
protected void SubmitButton_Click(object sender, EventArgs e)
{
ProductImages productImage = new ProductImages();
productImage.ProductID = Convert.ToInt32(ProductDropDownList.SelectedValue.ToString());
if (!FileUpload1.HasFile)
{
MessageLabel1.Text = "Please Select Image File"; //checking if file uploader has no file selected
}
else
{
int length = FileUpload1.PostedFile.ContentLength;
productImage.ProductImage = new byte[length];
FileUpload1.PostedFile.InputStream.Read(productImage.ProductImage, 0, length);
try
{
ProductImageBL.AddProductImages(productImage);
MessageLabel1.Text = "Product Image has been successfully added!";
}
catch (Exception ex)
{
MessageLabel1.Text = "Some error occured while processing the request. Error Description <br/>" + ex.Message;
}
}
}
图像压缩取决于图像类型和图像上的内容。现实生活中物体的照片通常是jpg格式的，你无法在不明显损失质量的情况下压缩它们。
可能你真正想做的是调整图像的大小，如500*500，如果你知道这将足以满足你的所有需求。请记住在调整大小时保存图像的宽高比。
相关问题:调整图片大小c#
dlxeon发布的SO链接非常棒。我自己用的例子。然而，所有这些例子调整图像的大小，但你也可以增加jpeg文件的压缩和'或降低DPI。
下面是一个如何调整和压缩jpeg的完整示例。它还会检查图像是否需要旋转，例如，如果手机被垂直握住。如果你想让图像正方形，你可以添加padding(内边距)
请注意，如果你使用这个例子是。png和。gif文件的透明度将丢失，因为他们被转换为jpg。
protected void SubmitButton_Click(object sender, EventArgs e)
{
if (FileUpload1.HasFile == true)
{
using (Bitmap postedImage = new Bitmap(FileUpload1.PostedFile.InputStream))
{
byte [] bin = Common.scaleImage(postedImage, 400, 400, false);
Image1.ImageUrl = "data:image/jpeg;base64," + Convert.ToBase64String(bin);
}
}
}
public static byte[] scaleImage(Image image, int maxWidth, int maxHeight, bool padImage)
{
try
{
int newWidth;
int newHeight;
byte[] returnArray;
//check if the image needs rotating (eg phone held vertical when taking a picture for example)
foreach (var prop in image.PropertyItems)
{
if (prop.Id == 0x0112)
{
int rotateValue = image.GetPropertyItem(prop.Id).Value[0];
RotateFlipType flipType = getRotateFlipType(rotateValue);
image.RotateFlip(flipType);
break;
}
}
//apply padding if needed
if (padImage == true)
{
image = applyPaddingToImage(image);
}
//check if the with or height of the image exceeds the maximum specified, if so calculate the new dimensions
if (image.Width > maxWidth || image.Height > maxHeight)
{
var ratioX = (double)maxWidth / image.Width;
var ratioY = (double)maxHeight / image.Height;
var ratio = Math.Min(ratioX, ratioY);
newWidth = (int)(image.Width * ratio);
newHeight = (int)(image.Height * ratio);
}
else
{
newWidth = image.Width;
newHeight = image.Height;
}
//start with a new image
var newImage = new Bitmap(newWidth, newHeight);
//set the new resolution, 72 is usually good enough for displaying images on monitors
newImage.SetResolution(72, 72);
//or use the original resolution
//newImage.SetResolution(image.HorizontalResolution, image.VerticalResolution);
//resize the image
using (var graphics = Graphics.FromImage(newImage))
{
graphics.CompositingMode = CompositingMode.SourceCopy;
graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.SmoothingMode = SmoothingMode.HighQuality;
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
graphics.DrawImage(image, 0, 0, newWidth, newHeight);
}
image = newImage;
//save the image to a memorystream to apply the compression level, higher compression = better quality = bigger images
using (MemoryStream ms = new MemoryStream())
{
EncoderParameters encoderParameters = new EncoderParameters(1);
encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, 80L);
image.Save(ms, getEncoderInfo("image/jpeg"), encoderParameters);
//save the stream as byte array
returnArray = ms.ToArray();
}
//cleanup
image.Dispose();
newImage.Dispose();
return returnArray;
}
catch (Exception ex)
{
//there was an error: ex.Message
return null;
}
}
private static ImageCodecInfo getEncoderInfo(string mimeType)
{
ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders();
for (int j = 0; j < encoders.Length; ++j)
{
if (encoders[j].MimeType.ToLower() == mimeType.ToLower())
return encoders[j];
}
return null;
}
private static Image applyPaddingToImage(Image image)
{
//get the maximum size of the image dimensions
int maxSize = Math.Max(image.Height, image.Width);
Size squareSize = new Size(maxSize, maxSize);
//create a new square image
Bitmap squareImage = new Bitmap(squareSize.Width, squareSize.Height);
using (Graphics graphics = Graphics.FromImage(squareImage))
{
//fill the new square with a color
graphics.FillRectangle(Brushes.Red, 0, 0, squareSize.Width, squareSize.Height);
graphics.CompositingMode = CompositingMode.SourceCopy;
graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.SmoothingMode = SmoothingMode.HighQuality;
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
//put the original image on top of the new square
graphics.DrawImage(image, (squareSize.Width / 2) - (image.Width / 2), (squareSize.Height / 2) - (image.Height / 2), image.Width, image.Height);
}
return squareImage;
}
private static RotateFlipType getRotateFlipType(int rotateValue)
{
RotateFlipType flipType = RotateFlipType.RotateNoneFlipNone;
switch (rotateValue)
{
case 1:
flipType = RotateFlipType.RotateNoneFlipNone;
break;
case 2:
flipType = RotateFlipType.RotateNoneFlipX;
break;
case 3:
flipType = RotateFlipType.Rotate180FlipNone;
break;
case 4:
flipType = RotateFlipType.Rotate180FlipX;
break;
case 5:
flipType = RotateFlipType.Rotate90FlipX;
break;
case 6:
flipType = RotateFlipType.Rotate90FlipNone;
break;
case 7:
flipType = RotateFlipType.Rotate270FlipX;
break;
case 8:
flipType = RotateFlipType.Rotate270FlipNone;
break;
default:
flipType = RotateFlipType.RotateNoneFlipNone;
break;
}
return flipType;
}