imshow() poor image quality

Hello

I have a GUI which is being used to display images. I have images in PNG format with resolution 3301x2550.

I have a simple GUI with 1 axes (axes1) and i am loading the images as follows:

myImage = imread(filename);

axes(handles.axes1);

imshow(myImage);

axis image;

When this loads in the GUI, however, the image quality is not good - here is an example. On the left is the image in the GUI, and on the right is the image loaded normally in windows at a similar magnitification - Note how the left image quality is significantly degraded

Is there a way I can get a better quality image in the GUI?

thanks!

Answer 1

[DGM]

Two things:

First, by default, imshow() uses nearest-neighbor interpolation for display. Things with fine features will be subject to this sort of aliasing.

% generate a grid of 1px wide lines
w = 301;
x = mod(1:w,10) == 1;
A = x | x';

% show the image
imshow(A)

In recent versions, you can specify a continuous display interpolant. While this may help for some images, images with regular patterns may still show some less-severe interference patterns.

% show the image with non-default display interpolation
imshow(A,'interpolation','bilinear')

Second, one has to ask why it's important that imshow() produces high-quality and accurate image displays. It's typically used for viewing.

Cases where it might be justified:

• Overlaying objects from plot(), contour(), patch() atop the image and then saving the figure/axes

Cases where people want to but really shouldn't:

• Displaying the image and then saving the figure/axes in order to save a copy of the image (use imwrite())
• Combining one or more images in the same figure and then saving the composite image (just composite them directly)

In cases where it's necessary to save the figure with a displayed image, tools like export_fig() (File Exchange) support antialiasing options which may help reduce the impact of any display limitations.