Blurry image when Resizing and Extending #1034

tomasr78 · 2021-09-28T07:16:59Z

tomasr78
Sep 28, 2021

I get blurry images in PDF when making them smaller and fitting to the PDF page in the center.

using (var imageCollection = new MagickImageCollection())
{
         imageCollection.Add(MagickImage(@"C:\myfile\jun_pdf_image.png"));
         imageCollection.Add(MagickImage(@"C:\myfile\original.jpg"));                                
         imageCollection.Write(@"C:\Projects\_temp\output.pdf");
}

 private static MagickImage MagickImage(string imageFile)
{
            var image = new MagickImage();
            var magickReadSettings = new MagickReadSettings();
            image.Read(imageFile, magickReadSettings);

            var fromPageSize = MagickGeometry.FromPageSize("a4");

            image.Resize(fromPageSize.Width, fromPageSize.Height);
            image.Extent(fromPageSize.Width, fromPageSize.Height, Gravity.Center);                                   

            image.Page = fromPageSize;

            return image;
}

If I remove the Resize and Extend methods then the images look sharp as original in PDF but then images are not centered in PDF. The Extend does not work without Resize and Resize produces a blurry image. Spends several hours to understand what's is causing blur in resized(downsized) images without any luck.

I have attached demo images and outputs, the output.pdf has centered but blurry images, the output-no-resize-no-extend.pdf has perfect quality images as I need the to images are no longer centered on the PDF page.

images.zip
output.pdf
output-no-resize-no-extend.pdf

Answered by dlemstra

Sep 28, 2021

When you resize the image you will make it smaller. When you want the best quality image you should only Extent the image. You should calculate what the width and height should be to have the same aspect ratio as the page size. You can calculate that with the following method (there might be a better method to do this):

var fromPageSize = MagickGeometry.FromPageSize("a4");

var width = image.Width / (double)fromPageSize.Width;
var height = image.Height / (double)fromPageSize.Height;
var max = Math.Max(width, height);
var newWidth = (int)(fromPageSize.Width * max);
var newHeight = (int)(fromPageSize.Height * max);

image.Extent(newWidth, newHeight, Gravity.Center);

View full answer

dlemstra · 2021-09-28T21:58:25Z

dlemstra
Sep 28, 2021
Maintainer

When you resize the image you will make it smaller. When you want the best quality image you should only Extent the image. You should calculate what the width and height should be to have the same aspect ratio as the page size. You can calculate that with the following method (there might be a better method to do this):

var fromPageSize = MagickGeometry.FromPageSize("a4");

var width = image.Width / (double)fromPageSize.Width;
var height = image.Height / (double)fromPageSize.Height;
var max = Math.Max(width, height);
var newWidth = (int)(fromPageSize.Width * max);
var newHeight = (int)(fromPageSize.Height * max);

image.Extent(newWidth, newHeight, Gravity.Center);

1 reply

sefakpsz Nov 19, 2024

If I don't use resize and extent method together I cannot fit my image into my canvas but when I do that it has blur. Here is my code that I applied:

           `using var bitmap = SKBitmap.FromImage(image);
            // using var image2 = new MagickImage(outputStream.ToArray());
            using var memoryStream = new MemoryStream();
            bitmap.Encode(memoryStream, SKEncodedImageFormat.Png, 100);
            memoryStream.Position = 0;

            using var magickImage = new MagickImage(memoryStream, new MagickReadSettings { Format = MagickFormat.Png, BackgroundColor = MagickColors.Transparent, AntiAlias = true });

            var width2 = magickImage.Width / canvasWidth;
            var height2 = magickImage.Height / canvasHeight;
            var max = Math.Max(width2, height2);
            var newWidth = canvasWidth * width2;
            var newHeight = canvasHeight * height2;

            magickImage.Extent((uint)newWidth, (uint)newHeight, Gravity.Center);
            magickImage.Resize((uint)width, (uint)height);

            using var resizedStream = new MemoryStream();
            magickImage.Write(resizedStream);
            resizedStream.Position = 0;

            using var resizedImage = SKBitmap.Decode(resizedStream);`

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Blurry image when Resizing and Extending #1034

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Blurry image when Resizing and Extending #1034

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tomasr78 Sep 28, 2021

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dlemstra Sep 28, 2021 Maintainer

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sefakpsz Nov 19, 2024

tomasr78
Sep 28, 2021

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dlemstra
Sep 28, 2021
Maintainer