I am trying to read pixels of a .bmp bitmap image using hex editor, but this bitmap image has a header file or something. I just need the R,G,B values of every pixel, like what I get in Matlab when I use the imread function. How long is the header file of a bitmap or where are the value of pixels located?
.BMP file? Wikipedia gives a very good description of header fields: http://en.wikipedia.org/wiki/BMP_file_format
Also see this. From that you can find About Bitmaps.
Related
I created a delphi component and want to load an image into it at runtime.
So i created a .RC file in notepad.
useIdentifer BITMAP "demo.BMP"
When i compiled the file it gave me an error "invalid bitmap format", so I did some research and got the solution that I had to check that the file is 8-bit, so I converted it to bitmap 256 colors using paint, but due to this i lost the quality and pixels of image.
I'm not sure how can i get rid of the error without losing quality of the image.
Use a PNG image instead of a BMP. The answer to this question will tell you how.
I done the following:
I made a screenshot of my linux desktop with gnome-screenshot then converted it to a bmp image and dumped it as raw hex values with xxd -ps.[resolution:969x1920]
From the bmp image i made before, i cropped a small area and exported it to another bmp image and dumped it as raw hex values as well with same method as before.[resolution:47x79]
Now when i go and copy a row of hex values (lets say from the end of the file just to avoid any headers) from the smaller image and try to find it on the other dumped file, it shows that there is not there.
I don't know much from image formats, i just want to know if there is something fundamental behind it that i am missing and i have to study before trying again something similar.
Thank you in advance!
I am trying to extract a whole scale image from a SVS file in C++.
I saw an explanation from the OpenSlide homepage.
It says the SVS format is "single-file pyramidal tiled TIFF".
So I tried to extract a whole-scale image like I did for TIFF image: I read all IFDs from the SVS file, but there is no 273 tag which contains an address pointing to a whole scale image.
That's why I am little confused now, the SVS format doesn't have a whole scale image inside the file?
I found an undefined private tag from a SVS file which number is 34675. Is this tag is for a whole scale image?
Or is there a proper way to extract it?
Aperio SVS is a tiled format. All levels of the pyramid are tiled images. The base layer is the first TIFF directory. This page of the LibTiff documentation shows how to read tiled images.
In short, you need to look for tag 324 (TIFFTAG_TILEOFFSETS), as well as tags 322 and 323 (TIFFTAG_TILEWIDTH, TIFFTAG_TILELENGTH). I highly recommend you use LibTiff for this, and don’t try to roll your own.
The custom tag in the SVS file contains metadata, including the physical size of a pixel in micron (SVS doesn’t set the resolution TIFF tags).
You can read out the thumbnail image (is this what you mean by whole scale image?) as an openslide associated image.
For example, libvips has a convenient openslide binding written by the openslide authors:
$ vipsheader -f slide-associated-images CMU-1.svs
label, macro, thumbnail
Lists the images in the SVS file. macro is the huge pyramid that you get by default, thumbnail is the small overview, label is the shot of the slide label.
Get the thumbnail like this:
$ vips copy CMU-1.svs[associated=thumbnail] x.jpg
To read as a JPG image.
In C++, you could write:
VImage thumb = VImage::new_from_file("CMU-1.svs",
VImage::option()->set("associated", "thumbnail"));
thumb.write_to_file("x.jpg");
I do imread image in Matlab, and it returns a 4-channel image:
im: 1012x972x4 uint8.
Which format is this image? How to check its color format(RGB, CMYK, etc)? I opened it in Gimp and the color profile is simply sRGB built-in
From imread() documentation:
The return value A is an array containing the image data. If the file
contains a grayscale image, A is an M-by-N array. If the file contains
a truecolor image, A is an M-by-N-by-3 array. For TIFF files
containing color images that use the CMYK color space, A is an
M-by-N-by-4 array. See TIFF in the Format-Specific Information section
for more information.
So the answer is apparently that this image's color space is CMYK.
If you want to check for a general input, then, from the same page:
To determine which color space is used, use imfinfo to get information
about the graphics file and look at the value of the
PhotometricInterpretation field.
Is there a way in matlab to convert an image file i.e; .png to .dat file?
It depends on the format of your .dat file. .dat is not a standard extension so you can get this from somewhere or design your own writer and reader. In terms of reading the .png you can just use matlabs imread('filename') function. This will return a NxMx3 matrix of the image and RGB values.
I would suggest combining the RGB values into a single float value and then using dlmwrite or csvwrite to store it. If you want to manipulate the image first that will be up to you.