验证 RGB 通道是否存在
Validate existance of RGB channels
我正在查看一些缺少方面的图像，即缺少红色、绿色或蓝色通道（在我提供图像之前，它们已被自动过程意外删除）。我需要对有效图像进行精细处理。
有没有一种快速检查图像是否具有所有三个（R、G 和 B）通道的方法？ Alpha 通道（如果包含）将被忽略。
在此之前，我一直在使用 PIL 进行 Python 点的图像处理（我意识到这可能不是前进的方向）。我还没有尝试任何东西，因为我不确定最好的前进方式：我的第一个猜测，这可能是冗长的，将遍历每个像素并计算出所有红色，绿色或蓝色数据是否为零（假定丢失）但是我感觉有一种更快的方法。
几乎所有图像处理库都提供读取像素值的方法。最简单和最有效的方法确实是遍历所有像素，检查所有像素的任何值是否为 0。
当然很多库也提供方便的工具来提取颜色平面和计算平均像素值。但在内部，它们除了遍历像素外什么都不做。如果不是通过检查每个值，任何算法还应该如何知道所有值是否为零？所以你的感觉是错误的，除非像素读取功能实现不佳并且算法使用更有效的东西，这是不太可能的。
所以无论哪种方式你都没有做错。
您可以使用 ImageMagick 轻松检查图像是否缺少通道。它安装在大多数 Linux 发行版上，可用于 OSX 和 Windows - 它也有 Python 绑定，但现在，我只使用命令行：
tl;dr
将红色通道的平均值、绿色通道的平均值和蓝色通道的平均值相乘 - 如果其中任何一个为零，则答案将为零，因此您的测试既快速又简单：
convert NormalImage.png -format '%[fx:mean.r*mean.g*mean.b]' info:
0.0284282
或
convert NoRed.jpg -format '%[fx:mean.r*mean.g*mean.b]' info:
0
加长版
基本上，您可以像这样获取图像统计信息：
identify -verbose main.png
Image: main.png
Format: PNG (Portable Network Graphics)
Mime type: image/png
Class: DirectClass
Geometry: 1790x4098+0+0
Units: Undefined
Type: TrueColor
Endianess: Undefined
Colorspace: sRGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
Pixels: 7335420
Red:
min: 0 (0)
max: 184 (0.721569)
mean: 139.605 (0.547471) <--- Useful
standard deviation: 76.5813 (0.300319)
kurtosis: -0.46531
skewness: -1.21572
entropy: 0.210465
Green:
min: 0 (0)
max: 115 (0.45098)
mean: 87.2562 (0.342181) <--- Useful
standard deviation: 47.864 (0.187702)
kurtosis: -0.465408
skewness: -1.21572
entropy: 0.223793
Blue:
min: 0 (0)
max: 51 (0.2)
mean: 38.6967 (0.151752) <--- Useful
standard deviation: 21.2286 (0.0832494)
kurtosis: -0.46556
skewness: -1.21571
entropy: 0.253787
Image statistics:
Overall:
min: 0 (0)
max: 184 (0.721569)
mean: 88.5193 (0.347134)
standard deviation: 53.5609 (0.210043)
kurtosis: 1.21045
skewness: 0.306884
entropy: 0.229348
Rendering intent: Perceptual
Gamma: 0.454545
Chromaticity:
red primary: (0.64,0.33)
green primary: (0.3,0.6)
blue primary: (0.15,0.06)
white point: (0.3127,0.329)
Background color: white
Border color: srgb(223,223,223)
Matte color: grey74
Transparent color: black
Interlace: None
Intensity: Undefined
Compose: Over
Page geometry: 1790x4098+0+0
Dispose: Undefined
Iterations: 0
Compression: Zip
Orientation: Undefined
Properties:
date:create: 2016-05-04T12:09:37+01:00
date:modify: 2016-05-04T12:00:06+01:00
png:bKGD: chunk was found (see Background color, above)
png:IHDR.bit-depth-orig: 8
png:IHDR.bit_depth: 8
png:IHDR.color-type-orig: 2
png:IHDR.color_type: 2 (Truecolor)
png:IHDR.interlace_method: 0 (Not interlaced)
png:IHDR.width,height: 1790, 4098
png:sRGB: intent=0 (Perceptual Intent)
signature: 1b12ce9d2a18826aa215b7e8b87a050717572ed638a6be6332c741eddb36c0be
Artifacts:
filename: main.png
verbose: true
Tainted: False
Filesize: 942KB
Number pixels: 7.335M
Pixels per second: 73.35MB
User time: 0.090u
Elapsed time: 0:01.099
Version: ImageMagick 6.9.3-7 Q16 x86_64 2016-04-05 http://www.imagemagick.org
或者，如果你喜欢解析 JSON:
convert main.png json:
{
"image": {
"name": "main.png",
"format": "PNG",
"formatDescription": "Portable Network Graphics",
"mimeType": "image/png",
"class": "DirectClass",
"geometry": {
"width": 1790,
"height": 4098,
"x": 0,
"y": 0
},
"units": "Undefined",
"type": "TrueColor",
"endianess": "Undefined",
"colorspace": "sRGB",
"depth": 8,
"baseDepth": 8,
"channelDepth": {
"red": 8,
"green": 8,
"blue": 8
},
"pixels": 7335420,
"imageStatistics": {
"all": {
"min": "0",
"max": "184",
"mean": "88.5193",
"standardDeviation": "53.5609",
"kurtosis": "1.21045",
"skewness": "0.306884"
}
},
"channelStatistics": {
"red": {
"min": "0",
"max": "184",
"mean": "139.605",
"standardDeviation": "76.5813",
"kurtosis": "-0.46531",
"skewness": "-1.21572"
},
"green": {
"min": "0",
"max": "115",
"mean": "87.2562",
"standardDeviation": "47.864",
"kurtosis": "-0.465408",
"skewness": "-1.21572"
},
"blue": {
"min": "0",
"max": "51",
"mean": "38.6967",
"standardDeviation": "21.2286",
"kurtosis": "-0.46556",
"skewness": "-1.21571"
}
},
"renderingIntent": "Perceptual",
"gamma": 0.454545,
"chromaticity": {
"redPrimary": {
"x": 0.64,
"y": 0.33
},
"greenPrimary": {
"x": 0.3,
"y": 0.6
},
"bluePrimary": {
"x": 0.15,
"y": 0.06
},
"whitePrimary": {
"x": 0.3127,
"y": 0.329
}
},
"backgroundColor": "#FFFFFF",
"borderColor": "#DFDFDF",
"matteColor": "#BDBDBD",
"transparentColor": "#000000",
"interlace": "None",
"intensity": "Undefined",
"compose": "Over",
"pageGeometry": {
"width": 1790,
"height": 4098,
"x": 0,
"y": 0
},
"dispose": "Undefined",
"iterations": 0,
"compression": "Zip",
"orientation": "Undefined",
"properties": {
"date:create": "2016-05-04T12:09:37+01:00",
"date:modify": "2016-05-04T12:00:06+01:00",
"png:bKGD": "chunk was found (see Background color, above)",
"png:IHDR.bit-depth-orig": "8",
"png:IHDR.bit_depth": "8",
"png:IHDR.color-type-orig": "2",
"png:IHDR.color_type": "2 (Truecolor)",
"png:IHDR.interlace_method": "0 (Not interlaced)",
"png:IHDR.width,height": "1790, 4098",
"png:sRGB": "intent=0 (Perceptual Intent)",
"signature": "1b12ce9d2a18826aa215b7e8b87a050717572ed638a6be6332c741eddb36c0be"
},
"artifacts": {
"filename": "main.png"
},
"tainted": false,
"filesize": "942KB",
"numberPixels": "7.335M",
"pixelsPerSecond": "73.35MB",
"userTime": "0.090u",
"elapsedTime": "0:01.099",
"version": "ImageMagick 6.9.3-7 Q16 x86_64 2016-04-05 http://www.imagemagick.org"
}
}
或者，你可以更手术，只得到你感兴趣的东西：
convert main.png -format '%[fx:255*mean.r]' info:
139.605
我正在查看一些缺少方面的图像，即缺少红色、绿色或蓝色通道（在我提供图像之前，它们已被自动过程意外删除）。我需要对有效图像进行精细处理。
有没有一种快速检查图像是否具有所有三个（R、G 和 B）通道的方法？ Alpha 通道（如果包含）将被忽略。
在此之前，我一直在使用 PIL 进行 Python 点的图像处理（我意识到这可能不是前进的方向）。我还没有尝试任何东西，因为我不确定最好的前进方式：我的第一个猜测，这可能是冗长的，将遍历每个像素并计算出所有红色，绿色或蓝色数据是否为零（假定丢失）但是我感觉有一种更快的方法。
几乎所有图像处理库都提供读取像素值的方法。最简单和最有效的方法确实是遍历所有像素，检查所有像素的任何值是否为 0。
当然很多库也提供方便的工具来提取颜色平面和计算平均像素值。但在内部，它们除了遍历像素外什么都不做。如果不是通过检查每个值，任何算法还应该如何知道所有值是否为零？所以你的感觉是错误的，除非像素读取功能实现不佳并且算法使用更有效的东西，这是不太可能的。
所以无论哪种方式你都没有做错。
您可以使用 ImageMagick 轻松检查图像是否缺少通道。它安装在大多数 Linux 发行版上，可用于 OSX 和 Windows - 它也有 Python 绑定，但现在，我只使用命令行：
tl;dr
将红色通道的平均值、绿色通道的平均值和蓝色通道的平均值相乘 - 如果其中任何一个为零，则答案将为零，因此您的测试既快速又简单：
convert NormalImage.png -format '%[fx:mean.r*mean.g*mean.b]' info:
0.0284282
或
convert NoRed.jpg -format '%[fx:mean.r*mean.g*mean.b]' info:
0
加长版
基本上，您可以像这样获取图像统计信息：
identify -verbose main.png
Image: main.png
Format: PNG (Portable Network Graphics)
Mime type: image/png
Class: DirectClass
Geometry: 1790x4098+0+0
Units: Undefined
Type: TrueColor
Endianess: Undefined
Colorspace: sRGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
Pixels: 7335420
Red:
min: 0 (0)
max: 184 (0.721569)
mean: 139.605 (0.547471) <--- Useful
standard deviation: 76.5813 (0.300319)
kurtosis: -0.46531
skewness: -1.21572
entropy: 0.210465
Green:
min: 0 (0)
max: 115 (0.45098)
mean: 87.2562 (0.342181) <--- Useful
standard deviation: 47.864 (0.187702)
kurtosis: -0.465408
skewness: -1.21572
entropy: 0.223793
Blue:
min: 0 (0)
max: 51 (0.2)
mean: 38.6967 (0.151752) <--- Useful
standard deviation: 21.2286 (0.0832494)
kurtosis: -0.46556
skewness: -1.21571
entropy: 0.253787
Image statistics:
Overall:
min: 0 (0)
max: 184 (0.721569)
mean: 88.5193 (0.347134)
standard deviation: 53.5609 (0.210043)
kurtosis: 1.21045
skewness: 0.306884
entropy: 0.229348
Rendering intent: Perceptual
Gamma: 0.454545
Chromaticity:
red primary: (0.64,0.33)
green primary: (0.3,0.6)
blue primary: (0.15,0.06)
white point: (0.3127,0.329)
Background color: white
Border color: srgb(223,223,223)
Matte color: grey74
Transparent color: black
Interlace: None
Intensity: Undefined
Compose: Over
Page geometry: 1790x4098+0+0
Dispose: Undefined
Iterations: 0
Compression: Zip
Orientation: Undefined
Properties:
date:create: 2016-05-04T12:09:37+01:00
date:modify: 2016-05-04T12:00:06+01:00
png:bKGD: chunk was found (see Background color, above)
png:IHDR.bit-depth-orig: 8
png:IHDR.bit_depth: 8
png:IHDR.color-type-orig: 2
png:IHDR.color_type: 2 (Truecolor)
png:IHDR.interlace_method: 0 (Not interlaced)
png:IHDR.width,height: 1790, 4098
png:sRGB: intent=0 (Perceptual Intent)
signature: 1b12ce9d2a18826aa215b7e8b87a050717572ed638a6be6332c741eddb36c0be
Artifacts:
filename: main.png
verbose: true
Tainted: False
Filesize: 942KB
Number pixels: 7.335M
Pixels per second: 73.35MB
User time: 0.090u
Elapsed time: 0:01.099
Version: ImageMagick 6.9.3-7 Q16 x86_64 2016-04-05 http://www.imagemagick.org
或者，如果你喜欢解析 JSON:
convert main.png json:
{
"image": {
"name": "main.png",
"format": "PNG",
"formatDescription": "Portable Network Graphics",
"mimeType": "image/png",
"class": "DirectClass",
"geometry": {
"width": 1790,
"height": 4098,
"x": 0,
"y": 0
},
"units": "Undefined",
"type": "TrueColor",
"endianess": "Undefined",
"colorspace": "sRGB",
"depth": 8,
"baseDepth": 8,
"channelDepth": {
"red": 8,
"green": 8,
"blue": 8
},
"pixels": 7335420,
"imageStatistics": {
"all": {
"min": "0",
"max": "184",
"mean": "88.5193",
"standardDeviation": "53.5609",
"kurtosis": "1.21045",
"skewness": "0.306884"
}
},
"channelStatistics": {
"red": {
"min": "0",
"max": "184",
"mean": "139.605",
"standardDeviation": "76.5813",
"kurtosis": "-0.46531",
"skewness": "-1.21572"
},
"green": {
"min": "0",
"max": "115",
"mean": "87.2562",
"standardDeviation": "47.864",
"kurtosis": "-0.465408",
"skewness": "-1.21572"
},
"blue": {
"min": "0",
"max": "51",
"mean": "38.6967",
"standardDeviation": "21.2286",
"kurtosis": "-0.46556",
"skewness": "-1.21571"
}
},
"renderingIntent": "Perceptual",
"gamma": 0.454545,
"chromaticity": {
"redPrimary": {
"x": 0.64,
"y": 0.33
},
"greenPrimary": {
"x": 0.3,
"y": 0.6
},
"bluePrimary": {
"x": 0.15,
"y": 0.06
},
"whitePrimary": {
"x": 0.3127,
"y": 0.329
}
},
"backgroundColor": "#FFFFFF",
"borderColor": "#DFDFDF",
"matteColor": "#BDBDBD",
"transparentColor": "#000000",
"interlace": "None",
"intensity": "Undefined",
"compose": "Over",
"pageGeometry": {
"width": 1790,
"height": 4098,
"x": 0,
"y": 0
},
"dispose": "Undefined",
"iterations": 0,
"compression": "Zip",
"orientation": "Undefined",
"properties": {
"date:create": "2016-05-04T12:09:37+01:00",
"date:modify": "2016-05-04T12:00:06+01:00",
"png:bKGD": "chunk was found (see Background color, above)",
"png:IHDR.bit-depth-orig": "8",
"png:IHDR.bit_depth": "8",
"png:IHDR.color-type-orig": "2",
"png:IHDR.color_type": "2 (Truecolor)",
"png:IHDR.interlace_method": "0 (Not interlaced)",
"png:IHDR.width,height": "1790, 4098",
"png:sRGB": "intent=0 (Perceptual Intent)",
"signature": "1b12ce9d2a18826aa215b7e8b87a050717572ed638a6be6332c741eddb36c0be"
},
"artifacts": {
"filename": "main.png"
},
"tainted": false,
"filesize": "942KB",
"numberPixels": "7.335M",
"pixelsPerSecond": "73.35MB",
"userTime": "0.090u",
"elapsedTime": "0:01.099",
"version": "ImageMagick 6.9.3-7 Q16 x86_64 2016-04-05 http://www.imagemagick.org"
}
}
或者，你可以更手术，只得到你感兴趣的东西：
convert main.png -format '%[fx:255*mean.r]' info:
139.605