将 tiff 像素长宽比更改为正方形

发布于 2024-07-20 12:54:52 字数 224 浏览 11 评论 0原文

我正在尝试对多页 tiff 文件执行条形码识别。但是 tiff 文件是从传真服务器（我无法控制）发送给我的，该服务器以非方形像素长宽比保存 tiff。这导致图像由于纵横比而被严重挤压。我需要将 tiff 转换为方形像素长宽比，但不知道如何在 C# 中执行此操作。我还需要拉伸图像，以便更改纵横比仍然使图像清晰可见。

有人用 C# 做过这个吗？或者有人使用过可以执行此类过程的图像库吗？

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羅雙樹 2024-07-27 12:54:52

如果其他人遇到同样的问题，这是我最终解决这个恼人问题的超级简单方法。

using System.Drawing;
using System.Drawing.Imaging;

// The memoryStream contains multi-page TIFF with different
// variable pixel aspect ratios.
using (Image img = Image.FromStream(memoryStream)) {
    Guid id = img.FrameDimensionsList[0];
    FrameDimension dimension = new FrameDimension(id);
    int totalFrame = img.GetFrameCount(dimension);
    for (int i = 0; i < totalFrame; i++) {
        img.SelectActiveFrame(dimension, i);

        // Faxed documents will have an non-square pixel aspect ratio.
        // If this is the case,adjust the height so that the
        // resulting pixels are square.
        int width = img.Width;
        int height = img.Height;
        if (img.VerticalResolution < img.HorizontalResolution) {
            height = (int)(height * img.HorizontalResolution / img.VerticalResolution);
        }

        bitmaps.Add(new Bitmap(img, new Size(width, height)));
    }
}

In case anyone else out there runs into the same issue, here is the super simple way I ended up fixing this annoying issue.

using System.Drawing;
using System.Drawing.Imaging;

// The memoryStream contains multi-page TIFF with different
// variable pixel aspect ratios.
using (Image img = Image.FromStream(memoryStream)) {
    Guid id = img.FrameDimensionsList[0];
    FrameDimension dimension = new FrameDimension(id);
    int totalFrame = img.GetFrameCount(dimension);
    for (int i = 0; i < totalFrame; i++) {
        img.SelectActiveFrame(dimension, i);

        // Faxed documents will have an non-square pixel aspect ratio.
        // If this is the case,adjust the height so that the
        // resulting pixels are square.
        int width = img.Width;
        int height = img.Height;
        if (img.VerticalResolution < img.HorizontalResolution) {
            height = (int)(height * img.HorizontalResolution / img.VerticalResolution);
        }

        bitmaps.Add(new Bitmap(img, new Size(width, height)));
    }
}

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后eg是否自 2024-07-27 12:54:52

哦，我忘记说了。 Bitmap.SetResolution 可能有助于解决宽高比问题。下面的内容只是关于调整大小。

请查看此页面。它讨论了两种调整大小的机制。我怀疑在你的情况下双线性过滤实际上是一个坏主意，因为你可能想要漂亮和单色的东西。

下面是简单的调整大小算法的副本（由 Christian Graus 编写，来自上面链接的页面），这应该是您想要的。

public static Bitmap Resize(Bitmap b, int nWidth, int nHeight)
{
    Bitmap bTemp = (Bitmap)b.Clone();
    b = new Bitmap(nWidth, nHeight, bTemp.PixelFormat);

    double nXFactor = (double)bTemp.Width/(double)nWidth;
    double nYFactor = (double)bTemp.Height/(double)nHeight;

    for (int x = 0; x < b.Width; ++x)
        for (int y = 0; y < b.Height; ++y)
            b.SetPixel(x, y, bTemp.GetPixel((int)(Math.Floor(x * nXFactor)),
                      (int)(Math.Floor(y * nYFactor))));

    return b;
}

另一种机制是滥用 GetThumbNailImage 函数，例如 this 。该代码保持了纵横比，但删除执行此操作的代码应该很简单。

Oh, I forgot to mention. Bitmap.SetResolution may help with the aspect ratio issues. The below stuff is just about resizing.

Check out This page. It discusses two mechanisms for resizing. I suspect in your case bilinear filtering is actually a bad idea, since you probably want things nice and monochrome.

Below is a copy of the naive resize algorithm (written by Christian Graus, from the page linked above), which should be what you want.

public static Bitmap Resize(Bitmap b, int nWidth, int nHeight)
{
    Bitmap bTemp = (Bitmap)b.Clone();
    b = new Bitmap(nWidth, nHeight, bTemp.PixelFormat);

    double nXFactor = (double)bTemp.Width/(double)nWidth;
    double nYFactor = (double)bTemp.Height/(double)nHeight;

    for (int x = 0; x < b.Width; ++x)
        for (int y = 0; y < b.Height; ++y)
            b.SetPixel(x, y, bTemp.GetPixel((int)(Math.Floor(x * nXFactor)),
                      (int)(Math.Floor(y * nYFactor))));

    return b;
}

An alternative mechanism is to abuse the GetThumbNailImage function like this. That code maintains aspect ratio, but removing the code that does that should be simple.

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