使用R的'jpeg'包创建图像不会产生预期的RGB值

Question

我在R中有一个带有这些值的3d矩阵：

mypixels=c(rep(1,8),rep(0,40))
mymatrix=array(mypixels,dim=c(4,4,3))
structure(mymatrix)
, , 1

     [,1] [,2] [,3] [,4]
[1,]    1    1    0    0
[2,]    1    1    0    0
[3,]    1    1    0    0
[4,]    1    1    0    0

, , 2

     [,1] [,2] [,3] [,4]
[1,]    0    0    0    0
[2,]    0    0    0    0
[3,]    0    0    0    0
[4,]    0    0    0    0

, , 3

     [,1] [,2] [,3] [,4]
[1,]    0    0    0    0
[2,]    0    0    0    0
[3,]    0    0    0    0
[4,]    0    0    0    0

应用此订单：

writeJPEG(mymatrix,"mypicture.jpg",quality = 1)

预计

将生成一半的红色图像，另一半生成黑色。但是，图像显示由四个不同的列组成，显示从红色到黑色的从左到右的渐变。事实上，阅读该图片显示：

mymatrix2=readJPEG("mypicture.jpg")
structure(mymatrix2)
, , 1

          [,1] [,2]      [,3] [,4]
[1,] 0.9960784  0.8 0.1490196    0
[2,] 0.9960784  0.8 0.1490196    0
[3,] 0.9960784  0.8 0.1490196    0
[4,] 0.9960784  0.8 0.1490196    0

, , 2

            [,1]       [,2] [,3]       [,4]
[1,] 0.007843137 0.08627451    0 0.01568627
[2,] 0.007843137 0.08627451    0 0.01568627
[3,] 0.007843137 0.08627451    0 0.01568627
[4,] 0.007843137 0.08627451    0 0.01568627

, , 3

     [,1]       [,2] [,3]       [,4]
[1,]    0 0.08235294    0 0.01568627
[2,]    0 0.08235294    0 0.01568627
[3,]    0 0.08235294    0 0.01568627
[4,]    0 0.08235294    0 0.01568627

将质量更改为0.5会产生类似的结果（尽管值略有不同）。那么，我怎样才能获得100％的质量，也就是说，在写入图像时没有改变颜色值？