Cannot convert images from png to pgm

I'm trying to convert png file to pgm file. I downloaded dragon.png and dragon.ascii.pgm from here

When I ran this code, it shows the image just fine:

oim = pgmRead('dragon.ascii.pgm');
figure;
showIm(oim);

When I try converting from png to pgm using imwrite:

img = imread('dragon.png');
imwrite(img, 'dragon.pgm', 'pgm', 'Encoding', 'ASCII');
oim = pgmRead('dragon.pgm');
figure;
showIm(oim);

The image shows up as some slanted lines. What am I doing wrong? Any help is appreciated.

Answer 1

[Image Analyst]

pgmread() does not appear to be a built-in MATLAB function - at least I don't have it in any of my toolboxes. I suggest you contact the author of pgmread() for guidance.

[Dao Lam]

Is there another way I can convert png to pgm then? Thanks!

My problem is that pgmRead works fine in the 1st case but not the 2nd case when I tried converting.

[Image Analyst]

Why don't you use imread()?