检查图像是否为灰度的可靠方法 [英] Reliable way to check if image is Grey scale

问题描述

我目前正在研究一个用例，需要确定上传的图像是灰度还是RGB。我发现了几种识别方法，但是不确定它们是否可靠，是否可以共同用于确认图像是否为灰度。

I am currently working on one use case where i need to determine if uploaded image is Grey Scale or RGB. I found couple of ways to identify this, but not sure if they are reliable and can be used collectively to confirm image is grey scale or not.

第1部分：读取图像

BufferedImage image = ImageIO.read(file);
        Raster ras = image.getRaster();
        int elem = ras.getNumDataElements();

我观察到elem的值在某些情况下为 1，但并非全部。

I observed value of elem is "1" in some cases, but not in all.

第2部分：检查每个像素的RGB值。如果R，G，B值与给定像素相同。

Part 2: Check RGB value of each pixel. If R , G, B value is same of given pixel.

BufferedImage image = ImageIO.read(file);
        Raster ras = image.getRaster();

        //Number of Color elements
        int elem = ras.getNumDataElements();

        int width = image.getWidth();
        int height = image.getHeight();

        int pixel,red, green, blue;

        for (int i = 0; i < width; i++)
            for (int j = 0; j < height; j++) {
                //scan through each pixel
                pixel = image.getRGB(i, j);
                red = (pixel >> 16) & 0xff;
                green = (pixel >> 8) & 0xff;
                blue = (pixel) & 0xff;

                //check if R=G=B
                if (red != green || green != blue ) {
                    flag = true;
                    break;
                }


            }

在这里我检查R，G，B值对于任何给定像素都是相同的，并且此行为在所有像素上都是一致的。

Here i check R, G,B values are same for any given pixel and this behavior is consistent across all pixels.

我正在使用这两种方法，但不确定它们的准确性如何。
请提出建议。

I am using these 2 approaches, but not sure how accurate they are. Kindly suggest..

推荐答案

下面的方法对我有用。谢谢大家的帮助。

Below approach is worked for me. Thanks guys for help.

BufferedImage image = ImageIO.read(file);
        Raster ras = image.getRaster();

        //Number of Color elements
        int elem = ras.getNumDataElements();

        int width = image.getWidth();
        int height = image.getHeight();

        int pixel,red, green, blue;

        for (int i = 0; i < width; i++)
            for (int j = 0; j < height; j++) {
                //scan through each pixel
                pixel = image.getRGB(i, j);
                red = (pixel >> 16) & 0xff;
                green = (pixel >> 8) & 0xff;
                blue = (pixel) & 0xff;

                //check if R=G=B
                if (red != green || green != blue ) {
                    flag = true;
                    break;
                }


            }

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