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C#圖片縮放裁切和WebApi應用

發表於 更新於 分類於 ， Disqus：

寫了一個圖片Resize的工具，但是後來發現如果用nginx好像根本不用寫…XDD
不過既然寫了就還是紀錄一下吧…也許未來哪天有機會用到

設定縮放或裁切的方式 - EnumModels.CutType

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public class EnumModels
{
    public enum CutType : int
    {
        自動 = 0,
        固定寬等比例縮放 = 1,
        固定高等比例縮放 = 2,
        固定寬高切中間 = 3
    }
}

主要邏輯 - ImageHelper

  • ResizeImage 縮放或裁切
  • BitmapToByte
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public class ImageHelper
{
    public static Bitmap ResizeImage(string imgPath, EnumModels.CutType cutType, int width = 0, int height = 0)
    {
        using (var imgBmp = new Bitmap(imgPath))
        {
            var oWidth = imgBmp.Width;
            var oHeight = imgBmp.Height;

            int oh, ow, x, y;
            if (cutType == EnumModels.CutType.自動)
            {
                if (width == 0 && height >= 0)
                    cutType = EnumModels.CutType.固定高等比例縮放;
                else if (height == 0 && width >= 0)
                    cutType = EnumModels.CutType.固定寬等比例縮放;
                else if (width >= 0 && height >= 0)
                    cutType = EnumModels.CutType.固定寬高切中間;
                else
                    throw new Exception("請指定正確的寬高");
            }
            switch (cutType)
            {
                case EnumModels.CutType.自動:
                    break;
                case EnumModels.CutType.固定寬等比例縮放:
                    if (width <= 0)
                        throw new Exception("寬度指定錯誤");
                    height = width * oHeight / oWidth;
                    break;
                case EnumModels.CutType.固定高等比例縮放:
                    if (height <= 0)
                        throw new Exception("高度指定錯誤");
                    width = height * oWidth / oHeight;
                    break;
                case EnumModels.CutType.固定寬高切中間:
                    if ((double)oWidth / (double)oHeight > (double)width / (double)height)
                    {
                        oh = oHeight;
                        ow = oHeight * width / height;
                        y = 0;
                        x = (oWidth - ow) / 2;
                    }
                    else
                    {
                        ow = oWidth;
                        oh = oWidth * height / width;
                        x = 0;
                        y = (oHeight - oh) / 2;
                    }
                    var cutBitmap = new Bitmap(width, height);
                    var graphics = Graphics.FromImage(cutBitmap);
                    graphics.DrawImage(imgBmp, new System.Drawing.Rectangle(0, 0, width, height),
                    new System.Drawing.Rectangle(x, y, ow, oh),
                    System.Drawing.GraphicsUnit.Pixel);
                    cutBitmap.SetResolution(72, 72);
                    return cutBitmap;
            }
            var newImg = new Bitmap(imgBmp, width, height);
            newImg.SetResolution(72, 72);
            return newImg;
        }
    }
    public static byte[] BitmapToByte(Bitmap bitmap)
    {
        using (var ms = new MemoryStream())
        {
            bitmap.Save(ms, ImageFormat.Jpeg);
            var bytes = ms.GetBuffer();
            return bytes;
        }
    }
}

.Net Core WebApi

  • OnPostUploadAsync: 上傳圖片存放至/wwwroot/UploadImage下
  • GetAll: 取得所有/wwwroot/UploadImage內的圖片
  • ResizeImage:
    • [Route(“w/{width}/{name}”)] : 固定寬等比例縮放
    • [Route(“h/{height}/{name}”)] : 固定高等比例縮放
    • [Route(“wh/{width}x{height}/{name}”)] : 固定寬高切中間
  • MemoryCache: 避免重複使用浪費時間，記得在Startup.cs加上services.AddMemoryCache();
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    [Route("api/[controller]")]
    [ApiController]
    public class ImageController : ControllerBase
    {
        private readonly IHostingEnvironment _hostingEnvironment;
        private readonly IMemoryCache _memoryCache;
        private static string IMAGE_UPLOAD_CURRENT_PATH;
        public ImageController (IHostingEnvironment hostingEnvironment, IMemoryCache memoryCache)
        {
            _hostingEnvironment = hostingEnvironment;
            _memoryCache = memoryCache;
            if (IMAGE_UPLOAD_CURRENT_PATH == null)
            {
                IMAGE_UPLOAD_CURRENT_PATH = Path.Combine(_hostingEnvironment.ContentRootPath, "wwwroot", "UploadImage");
                if (System.IO.Directory.Exists(IMAGE_UPLOAD_CURRENT_PATH))
                    System.IO.Directory.CreateDirectory(IMAGE_UPLOAD_CURRENT_PATH);
            }
        }

        [HttpPost, Route("Upload")]
        public async Task<IActionResult> OnPostUploadAsync([FromForm(Name = "image")]List<IFormFile> files)
        {
            long size = files.Sum(f => f.Length);
            
            foreach (var formFile in files)
            {
                if (formFile.Length > 0)
                {
                    var filePath = Path.Combine(IMAGE_UPLOAD_CURRENT_PATH, formFile.FileName);
                    if (System.IO.File.Exists(filePath))
                    {
                        return BadRequest($"檔案已存在, { formFile.FileName }");
                    }
                    using (var stream = System.IO.File.Create(filePath))
                    {
                        await formFile.CopyToAsync(stream);
                    }
                }
            }
            return Ok(new { count = files.Count, size });
        }

        [HttpGet, Route("GetAll")]
        public IActionResult GetAll()
        {
            var imgFiles = _memoryCache.Get(CacheKey.UPLOAD_IMAGE_FILES) as IEnumerable<string>;
            if (imgFiles == null)
            {
                imgFiles = Directory.GetFiles(IMAGE_UPLOAD_CURRENT_PATH).Select(x => Path.GetFileName(x));
                _memoryCache.Set(CacheKey.UPLOAD_IMAGE_FILES, imgFiles);
            }
            return Ok(new {
                code = 20000,
                data = imgFiles 
            });
        }

        #region ResizeImage
        [HttpGet]
        [Route("w/{width}/{name}")]
        [Route("h/{height}/{name}")]
        [Route("wh/{width}x{height}/{name}")]
        public IActionResult GetResizeImage(int width, int height, string name, int cutType = 0)
        {
            try
            {
                var imgPath = Path.Combine(IMAGE_UPLOAD_CURRENT_PATH, name);
                var imgType = Path.GetExtension(name).Replace(".", "").ToLower();
                var contentTypeStr = ImageType.GetTypeByFileExtension(imgType);
                //圖片不存在
                if (!new FileInfo(imgPath).Exists)
                    throw new Exception("圖片不存在");

                var bitmap = ImageHelper.ResizeImage(imgPath, (EnumModels.CutType)cutType, width, height);
                return new FileContentResult(ImageHelper.BitmapToByte(bitmap), contentTypeStr);
            }
            catch //(Exception ex)
            {
                return NotFound();
            }            
        }
        #endregion
    }

最後，如果你有興趣學程式，可以參考下列平台:

  1. HiSKIO
  2. Udemy

裡面有很多豐富的課程，線上學習，不用出門唷！

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