bmp file issues

[steve]

I am reading in a bitmap file using the microsoft bmp classes and most
all of the files are as follows

Width :640:
Height :480:
Bits :8:
Upside Down :1:
Core :0:
Palette Size :256:
Compression :0:

and are indexed images. Using fread and fseek to pull off the header
and start reading at the first pixel. When I get the indexed pixel
values and compare them to values in Photoshop they do not match. I
have read that bitmaps are "upside down". Do I need to flip things
around? I am assuming the header is 1077 bytes (0x0 through 0x436).

Thanks

 

[Bartc]

I am reading in a bitmap file using the microsoft bmp classes and most
all of the files are as follows

Width :640:
Height :480:
Bits :8:
Upside Down :1:
Core :0:
Palette Size :256:
Compression :0:

and are indexed images. Using fread and fseek to pull off the header
and start reading at the first pixel. When I get the indexed pixel
values and compare them to values in Photoshop they do not match. I
have read that bitmaps are "upside down". Do I need to flip things
around? I am assuming the header is 1077 bytes (0x0 through 0x436).

I make that 1078 bytes: 54 header stuff and 256x4 bytes of palette data.

In what way do the values not match? Is Photoshop giving you 8-bit pixel
values, or converting these to RGB?

There is some confusion sometimes with RGB order, some parts might use BGR.

The upside down flag is to do with whether the first scan line comes first,
or last. If the latter, and you are comparing pixel (0,0), then it might
well give a mismatch, as Photoshop will likely flip the image automatically.

 

[Barry Schwarz]

I am reading in a bitmap file using the microsoft bmp classes and most
all of the files are as follows

C supports classes?

Width :640:
Height :480:
Bits :8:
Upside Down :1:
Core :0:
Palette Size :256:
Compression :0:

and are indexed images. Using fread and fseek to pull off the header
and start reading at the first pixel. When I get the indexed pixel
values and compare them to values in Photoshop they do not match. I
have read that bitmaps are "upside down". Do I need to flip things
around? I am assuming the header is 1077 bytes (0x0 through 0x436).

And your question about the C language (as opposed to your program
logic) is?