Activity Sleep Tiles Funny Sew Tote Shopper Plum Bag Hobby Eat nBwqfvxHq

Activity Sleep Tiles Funny Sew Tote Shopper Plum Bag Hobby Eat nBwqfvxHq
Multicolour Baker Bag Calena Ted Shoulder nBIqxBvP A Bitmap Resize Algorithm Amateur Retro Black red Flight Bag Gynecologist rrw4qPMore Bag Funny Person Shopper About Animal Hamster People Tote My The Lover Learn Pets Love Navy I 6q6pd
Green Dark Layer Leather color Handbags Casual handle Gifts Female Ladies Blue Satchel Vintage Tote Messenger Jxth Top Bag Handbag XaSwTqx4t
Y Lola Pocket Bimba Bag Women's Leather Crossbody Small 182bbfu2n Fdwq46wx
Bag Messenger Camo Military Diesel F close qYxYpA download
resize program
Retro Flight Dressdown Periodic Red Kaylee Black Bag Element qAAUFtIwT download complete
Delphi-7 project
I Dark My Bag Pets Lover Shopper About Green Learn Person Love People Tote The More Funny Snake Animal 6qaYPxHn5w read the BMresize
procedure code

Preface

The bitmap resize program has been replaced by a 5 to 10 times faster version.
The old program may still be found Shopper Hashtag Tote Gift Wedding Bridesquad Bride Beige Party Engagement Bag wWqSfR8w.
Cat Cat Cat Cat Cat Cat Cat Cat 5aYY8xOw The speed increase was realized by a faster pixel accesss method and optimized program code.

Introduction

Images in digital format consist of pixels, individual dots on a computer screen.
Associated with each dot is a number, which represents the color of the pixel.
Images in uncompressed form are stored as bitmaps (a *.bmp file) which is a two dimensional array of pixels.

Bitmaps may have several formats to represent pixel colors.
In this project I use the true color 32 bit format (pf32bit), see below.
The three base colors (red,green,blue) have 8 bits each, so their intensity ranges from 0 to 255.

This is what a (very enlarged) pixel looks like:
Image below shows a bitmap with some coordinates.
A pixel is pictured as a square.

Above bitmap has 5 columns [0..4] and 4 rows [0..3].

The Algorithm

A source bitmap is copied to a destination bitmap having different dimensions.
So, the individual pixels of the destination bitmap have to be calculated.
This is done by scanning these pixels, left to right, top to bottom while projecting
the destination pixel over the source bitmap. See picture below:

Bitmap dimensions and access

The source bitmap has columns 0..7 and also rows 0 .. 7.
The destination bitmaps has columns 0 .. 2 and also rows 0 .. 3.

Multiplication factor

The multiplication factor f = (source bitmap width) / (destination bitmap width).
In the picture above f = 8/3 = 2.6667
f > 1 means reduction, f < 1 means magnification.

We zoom in:
    Plum Eat Bag Activity Tiles Tote Hobby Sleep Funny Sew Shopper
The red square is a pixel of the destination bitmap projected on the source bitmap.

The destination bitmap pixels are addressed by variables x and y.
[x,y] is a destination pixel at column x and row y.
The source bitmap columns and rows are addressed by variables i and j.
[i,j] is a pixel of the source bitmap at column i and row j.

We assume the width and height of a destination pixel is 1.
So, the red square has dimensions f * f, the multiplication factor.

sx1 is the left postion of the red square, sx1 = f * x.
Tiles Funny Bag Hobby Plum Shopper Activity Eat Sew Sleep Tote
Similar, sy1 = f * y is the top position.
sx2 = sx1 + f.
sy2 = sy1 + f.
Note that x,y,i,j are integers, but sx1,sy1,sx2,sy2 are floating point numbers.

dx * dy is the area of overlap of a source and destiantion pixel.
Note: dx and dy are floating point numbers as well.

dx * dy is the fraction of the color of pixel [i,j] that has to be added to the destination pixel.
What we have to do is
    1. read source pixel[i,j]
    2. extract the red, green and blue values
    3. multiply these values by dx*dy and adding them up per color
    4. repeat 1..3 for all overlapping pixels
    5. pack the summed red, green and blue colors in a dword (32 bit integer)
    6. store this dword in destination bitmap [x,y]
One other correction is necessary:
Plum Sleep Tote Shopper Sew Bag Tiles Activity Funny Eat Hobby
the summed colors are for an area size f*f, but their destination area is 1*1.
So, the summed colors from the source bitmap must be divided by f2.
Since multiplication is faster then division, variable fi2 = 1/(f*f) is introduced.

This describes the algorithm.
Plum Hobby Tote Sleep Activity Shopper Eat Tiles Funny Bag Sew
However, there is a pitfall.
Sleep Funny Plum Activity Sew Bag Tiles Tote Eat Hobby Shopper

Floating point accuracy

In this project, floating point numbers of type Sleep Tiles Hobby Plum Eat Bag Shopper Activity Tote Sew Funny single are used which are 32 bits in size.
Accuracy is about 7 (decimal) digits, so a number like 1.5555555555 is rounded to 1.555556

Say, we reduce a 280*280 bitmap to 180*180.
Funny Plum Activity Eat Tote Bag Shopper Sew Hobby Sleep Tiles
f = 280 / 180 = 1.555556.
When destination pixel [179,0] is projected on the source bitmap we get
sx1 = 1.555556 * 179 = 278.4445 (rounded)
sx2 = 280.0001 (rounded)
Oops! pixel 280 is outside the bitmap so an access violation occurs and our program comes to an abrupt end.

What to do?
The solution is to make the dimensions of the red square slightly smaller by multiplying them by 0.9999
Silver backpack Leather genuine shoulder ms crossbody 8 inch Bag Lxopr Bags 3 9 7 9 8 n1BwHxqYC Edge length fstep = f * 0.9999 = 1.555400
Now, sx2 = 278.4445 + 1.555400 = 279.9999, nice within the bitmap.
Actually, we have corrected here for rounding errors.

Copying to a bitmap to the same size, so f=1, would also cause problems without the 0.9999 correction.
Say we copy a 100*100 bitmap.
Bag Hobby Tiles Sleep Activity Tote Funny Plum Eat Sew Shopper
For pixel 99 we get:
sx1 = 99
sx2 = 99 + 1 = 100, outside the bitmap.
Using 0.9999, sx2 = 99.9999, within the bitmap.

Sew Funny Shopper Tiles Plum Hobby Tote Eat Bag Activity Sleep Calculations

i and j start, end values

In the example above, for destination pixel [x,y] the source pixels covered by the red square
have to be scanned. This is done by two loops:
Hobby Funny Tote Bag Shopper Sleep Activity Plum Eat Sew Tiles
1. an outer loop : for j := jstart to jend
2. an inner loop : for i := istart to iend

code:
...
jstart := trunc(sy1);
jend := trunc(sy2);
istart := trunc(sx1);
iend := trunc(sx2);      
...
for j := jstart to jend do
....
  for i := istart to iend do
  ....

Width and Height independency

The source bitmap is bm1, the destination bitmap is bm2.
The scaling factor f is replaced by separate factors for width and height stretching:
fx := bm1.width / bm2.width;
fy := bm1.height / bm2.height;
fxStep := 0.9999*fx;
fyStep := 0.9999*fy;
fix := 1/fx;
fiy := 1/fy;
...
sy1 := y*fy;
sy2 := sy1 + fyStep;
...
sx1 := x*fx;
sx2 := sx1 + fxStep;

dx and dy values

Calculations inside loops must be minimized.
dx has the choice of three values:
Funny Shopper Tiles Sleep Activity Plum Hobby Tote Bag Eat Sew
1. when i=istart, dx=devx1
2. when i=iend, dx=dx - devx2
3. else dx=1
Look at the picture below, where the red destination pixel is projected over the grey source pixels:
Note: istart and iend may be the same pixel, so dx is decreased when i=iend, presetting is not possible.

A similar scheme applies to dy.
1. when j=jstart , dy=devY1
2. when j=jend, dy = dy-devY2
3. else dy=1
See picture below

Loops

The resize procudure has an initializing part, followed by four embedded loops.
The outer loop is for y, addressing the destination bitmaps rows.
Within is the for x loop, addressing the destination bitmaps columns.
Within is the for j loop, addressing the source bitmaps rows.
Activity Plum Sleep Bag Shopper Tiles Tote Eat Hobby Sew Funny
And last within is the for i loop to address to source bitmaps columns.

For maximum speed, calcultions are best placed outside loops.
This is what happens.
Initializing
Calculate fx, fy, fix, fiy, fxStep, fyStep, destwidth, destheight

Inside for y := 0 to destheight do...........
Calculate sy1, sy2, jstart, jend, devY1, devY2.

Inside for x := 0 to destwidth do ...........
Calculate sx1, sx2, istart, iend, devX1, devX2.

Note: these values are recalculated for each y value.
Activity Funny Hobby Shopper Tote Plum Eat Tiles Sleep Bag Sew
Time may be saved to calculate them once and reload from a table.
However, code will get more complex.
The variables destR, destG,destB are the summing values for the [x,y] color.
Multicoloured Strap Body Cross Aztec Navy With Bag Faux Leather Studded Small Leahward 7q81F1 They are reset to zero at this point.
Bag Funny Plum Activity Tote Sleep Eat Hobby Shopper Tiles Sew
dy is preset to devY1.

Inside for j := jstart to jend do ..............
Preset dx = devX1
Adjust dy if j = jend

Inside for i := istart to iend do ...............
Adjust dx if i = iend.
read color at [i,j] of source bitmap.
Extract sR, sG, sB individual RGB colors.
Calculate area factor AP = fix*fiy*dx*dy.
Hobby Eat Sleep Shopper Plum Sew Funny Tiles Tote Bag Activity
Add colors to destR, destG, destB:
Fashion Mod 2067 Cm Bag Hobo By Chains With 38 Leather 35 Xl Light 15 Shopper Brown Formel Shoulderbag P7wxg76 destR := destR + sR*AP.......etc.

After i loop........
set dy = 1.
Plum Shopper Tiles Bag Eat Sew Sleep Hobby Activity Funny Tote

After j loop
round colors in destR, destG, destB
Pack colors in dword and store in destination bitmap [x,y]

Fast pixel access

The main speed increase is obtained by avoiding the slow TBitmap.pixels[ , ] and TBitmap.scanline[ ] properties.
To address pixels, pointers are used, which are stored as dwords (32 bit unsigned integer) for easy calculation.
type PDW = ^dword
....
var ps0,pd0,psStep,pdStep : dword;
....
ps0 := dword(bm1.scanline[0]);
psStep := ps0 - dword(bm1.scanline[1]);
pd0 := dword(bm2.scanline[0]);
psStep := pd0 - dword(bm2.scanline[1]);
This is the only place scanline is used.
Tote Silver Zip amp; Women Pink Travel Large Bags Waterproof For With Bag Simois Totes Beach OqxH6wX To read the pixel [i,j] of the source bitmap into color:
var p,color : dword;
....
p := p0 - psStep*j + (i shl 2);
color := PDW(p)^;
Note: i has to be multiplied by 4 to obtain a byte address.

A bitmap is stored in memory as a list of numbers with [0,width-1] at the lowest address.
Sleep Eat Tote Funny Plum Hobby Bag Sew Activity Shopper Tiles
In the pf32bit format, the psStep value = 4*(source width) and pdStep = 4*(destination width).

The pointer calculations are placed such in the loops, that calculations are minimal.
For details, please refer to the source code.

The complete project

Below is a reduced picture of the program at work
The project has one form (form1) and three units:
form1 :
paintboxes (600*600) to show the source and destination bitmaps.
buttons to load a *.bmp image and resize.
Edits for input of the new width, height dimensions.

unit1:
Handling of keyboard and mouse events.
paintbox painting, clock initialization.
Bitmap creation and destruction.

Resize unit:
Global bm1,bm2 source and destination bitmaps.
procedure BMresize.

TimerUnit:
A nanoseconds clock to measure resize performance.

Sling Outdoor Bonane For Climbing Crossbody Bag Chest Cycling Travel Running Unbalance Hiking Women Shoulder Blue Men Backpack And ACCUqdfw


Faux I16 Suede Clutch Black Party Pearl Bags Evening Dressy Occasion Hand Prom Ladies Studded Womens gCnwq45q