mathlab image processing

>> img=imread('img01.tif');
>> img1=imread('img01.tif');

>> imwrite(img1,'Im01.png','png');
>> whos img1
Name        Size                 Bytes  Class    Attributes

img1      600x591x3            1063800  uint8

>> img2=imread('im01.png');
>> whos im2

>> imfinfo('img01.tif')

ans =

Filename: 'img01.tif'
FileModDate: '01-Февруари-2010 15:57:00'
FileSize: 717940
Format: 'tif'
FormatVersion: []
Width: 591
Height: 600
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: [73 73 42 0]
ByteOrder: 'little-endian'
NewSubFileType: 0
BitsPerSample: [8 8 8]
Compression: 'LZW'
PhotometricInterpretation: 'RGB'
StripOffsets: [5x1 double]
SamplesPerPixel: 3
RowsPerStrip: 147
StripByteCounts: [5x1 double]
XResolution: 100
YResolution: 100
ResolutionUnit: 'Inch'
Colormap: []
PlanarConfiguration: 'Chunky'
TileWidth: []
TileLength: []
TileOffsets: []
TileByteCounts: []
Orientation: 1
FillOrder: 1
GrayResponseUnit: 0.0100
MaxSampleValue: [255 255 255]
MinSampleValue: 0
Thresholding: 1
Software: 'Adobe Photoshop CS3 Windows '
DateTime: '2010:02:01 15:56:53 '
ICCProfileOffset: 26718

>> img1.info=imfinfo('img01.tif');

>> img.bytes=img1.info.Width*img1.info.Height*img1.info.BitDepth;
>> img.filesize=img1.info.FileSize

img =

bytes: 8510400
filesize: 717940

>> img.bytes=img1.info.Width*img1.info.Height*img1.info.BitDepth;
>> img.filesize=img1.info.FileSize;