Matlab写/读图的问题?

math618

img(:,:,1)=round(rand(5)*255);
img(:,:,2)=round(rand(5)*255);
img(:,:,3)=round(rand(5)*255);
imwrite(img,'rand.bmp','bmp')
a=imread('rand.bmp','bmp');

为什么img和a的值不同？

下天

请详细阅读imwrite的help：
  if the (input) data array is double, the assumed dynamic range is [0,1]

  语句"round(rand(5)*255)"，使得double型变量img中几乎所有数据都大于1，超出了动态范围，故而得到的Unit8型变量a中几乎所有数据都为255。

  根据help中的说明：
  For ...RGB images, if the data array is double, the assumed dynamic range is [0,1].  The data array is automatically scaled by 255 before being written out as uint8.  ...If logical data is written to a BMP, ...it is assumed to be a binary image and will be written with a
bitdepth of 1.
  修改程序如下：
  img(:,:,1)=rand(5);
  img(:,:,2)=rand(5);
  img(:,:,3)=rand(5);
  imwrite(img,'rand.bmp','bmp')
  a=imread('rand.bmp','bmp');
  数值上，a=floor(img*255)+1

  如果输入的是unit8或unit16型的img的话，就更容易了

  详细内容参见imwrite、imread的help文件中的Date Types

shaojie

这是imwrite的帮助文件：
IMWRITE(A,FILENAME,FMT) writes the image A to FILENAME.
    FILENAME is a string that specifies the name of the output
    file, and FMT is a string the specifies the format of the
    file.  A can be either a grayscale image (M-by-N) or a
    truecolor image (M-by-N-by-3).

下天

不止这么少吧