Gaussian blur-
Functions -
1.iir_young_find_constants (gfloat sigma, gdouble *B, gdouble *b) -
Based on sigma( standard deviation of Gaussian distribution ) we calculate the constants. If sigma == 0 then to prevent ringing at the tile boundaries we define *B = 1 and b[0]=1,b[1]=b[2]=b[3]=0 else the value of the constants depend upon the parameter 'q'.
2. iir_young_blur_1D (gfloat * buf,gint offset, gint delta_offset, gdouble B, gdouble * b, gfloat *w, gint w_len)-
in the forward filter we increase the offset every time we iterate by an amount = delta_offset till we reach the end.
In backward filter we begin from the other extreme and every time we iterate to the left we decrease the offset by an amount = delta_offset
3. iir_young_hor_blur (GeglBuffer *src, const GeglRectangle *src_rect,GeglBuffer *dst,const GeglRectangle *dst_rect, gdouble B, gdouble *b) -
This is for INFINITE IMPULSE RESPONSE.Produces the horizontal blurring in the image.It expects the source and destination to be of same height and 0 y offset.
4. iir_young_ver_blur (GeglBuffer *src, const GeglRectangle *src_rect,GeglBuffer *dst,const GeglRectangle *dst_rect, gdouble B, gdouble *b) -
This is for INFINITE IMPULSE RESPONSE.Produces the vertical blurring in the image.It expects the source and destination to be of same width and 0 x offset.
5. fir_calc_convolve_matrix_length (gdouble sigma) -
calculates the length of convolution matrix depending upon the standard deviation.
6. fir_gen_convolve_matrix (gdouble sigma, gdouble **cmatrix_p) -
produces the convolution matrix cmatrix_p which is applied to the original image to produce gaussian blur.Each pixel's new value is set to a weighted average of that pixel's neighborhood. The original pixel's value receives the heaviest weight (having the highest Gaussian value) and neighboring pixels receive smaller weights as their distance to the original pixel increases.
7. fir_young_hor_blur (GeglBuffer *src, const GeglRectangle *src_rect,GeglBuffer *dst,const GeglRectangle *dst_rect, gdouble B, gdouble *b) -
Calculates horizontal blur for FINITE IMPULSE RESPONSE.It expects the source and destination to be of same height and 0 y offset.
8. fir_young_ver_blur (GeglBuffer *src, const GeglRectangle *src_rect,GeglBuffer *dst,const GeglRectangle *dst_rect, gdouble B, gdouble *b) -
Calculates vertical blur for FINITE IMPULSE RESPONSE.It expects the source and destination to be of same width and 0 x offset.
9.process (GeglOperation *operation, GeglBuffer *input,GeglBuffer *output, const GeglRectangle *result)-
GeglOperationAreaFilter base class allows defining operations where output data depends upon a neighbourhood with an input window that extends beyond the output window, the information about needed extra pixels in different directions should be set up in the prepare callback for the operation.Based on 'iir' or 'fir' it blurifies the image first horizontally and then vertically with different sets of functions used for both cases.
Extras -
Cartoon -
header file - libgimp/gimp.h makes all basic plugin elements available to us.
Structures defined-
1. CartoonVals - holds parameters - mask_radius,threshold,pct_black
mask_radius - size of area the filter works upon
threshold - relative intensity difference which will result in darkening
pct_black - decides the amount of black color added to the image
Local Variables -
1. cvals - storing default values for the parameters of the structure CartoonVals.
2. GimpPlugInInfo PLUG_IN_INFO - Contains four pointers to different functions which are called during plugin execution.
a)init - optional(can have null value) and is called as GIMP starts up. It can be called if we want to register some procedure conditionally on some files prescence.
b)quit - also optional( can have null value ) and is called when GIMP is going to close.
c)query - called when the plugin comes into existence or every time when it is modified.
d)run - it is the plugin processing function which receives the plugin name, input parameters, number of return values, pointer to output parameters.
MAIN() - it is a macro defined for calling the initialisation and calling appropriate functions that our plugin needs during its life time.
Functions -
1. query() - defines the input arguments
Structure GimpParamDef contains - type, name and description.
It registers the function in the path specified as here under "<Image>/Filters/Artistic"
2. cartoon_dialog (GimpDrawable *drawable) -
opens a dialog box for the user for specifying the basic input parameters. This also function holds the basic layout informaion for the dialog box. It clearly mentions the existence of two scale bars ( mask radius, percent black ), preview window and ok button. User can change the value of parameters and have a preview for every changed argument.The widget does not gets destroyed until the ok button( signal - GTK_RESPONSE_OK ) or cancel button is pressed and the final parameters are then saved.
3. cartoon(GimpDrawable *drawable,GimpPreview *preview) -
Every variable of the GimpDrawable struct has a drawable id, width, height,bytes per pixel,number of tile rows, number of tile columns, normal tiles and shadow tiles. Here we check if the drawable has an alpha channel associated with it. Alpha channel can be there with the layer types such as RGB, GRAYSCALE and it defines the amount of opacity of the layer.
Initialise 7 memory locations val_p1,val_p2,val_m1,val_m2,src,dest1,dest2. Initialise the pixel region pointed by 'src_rgn', new region being attached to drawable region,(0,0) as initial coordinates, width as drawable->width, height as drawable->height.
It then calculates the standard deviations - blur radius and mask radius. Now calculate the value of needed constants from the 'Gaussian-blur helper function' - find_constants.
Start the analysis of image by taking vertical strips into consideration begining from column 0 till width. gimp_pixel_rgn_get_col(col+x1, y1 ) gets all pixels in a column from (col+x1,y1) to (col+x1, y1+height-1 ) and fills the buffer src with it.sp_p1 holds the value for first pixel and sp_m1 holds the value for the last pixel and with these values and the values calculated by the find_constants functions we calculate every pixel along a column and then use the user defined function 'transfer_pixels' to transfer these pixel to the destination. gimp_progress_update() updates the progress bar for the current plugin.
Similary we analyse it now by taking horizontal strips begining from row 0 to row height.Initialise 4 memory locations for holding the values, 2 for the source buffer( src1, src2 ).Initialise the initial pixels i.e the starting row pixel 0 and width-1 and with the help of the values calculated from the gaussian function calculate every pixel along a row and use transfer_pixels() function to transfer these pixels to the destination.
Thus we first move column-wise and then row-wise to analyse every pixel.
Compute the ramp value which sets 'pct_black' % of the darkened pixels black.Initialise and register the pixel region . dest1 deals with the calculations for blur radius and dest2 deals with the calculations for the mask radius.For every pixel calculate the diff as the ratio of the blur intensity to that of the average intensity.if the difference > threshold then multiplying factor = 1 else check if ramp != 0 then mult = (ramp - MIN (ramp, (cvals.threshold - diff))) / ramp. The final intensity for every pixel calculated as blur_ptr[col]*mult is CLAMPED between 0 to 255. If number of bytes per pixel is less than 3 then initialise denstination pixels directly and transfer the alpha value as well if the source has any. Otherwise if( bpp > 3 ) i.e RGB layers exist then convert the RGB values to the corresponding HLS values.
R[0-255](Red) G[0-255](Green) B[0-255](Blue)
H[0-360](Hue) L[0-255](Lightness) S[0-255](Saturation)
With it we set the lightness and again convert back the to RGB
And after it we merge the shadow tile and update the drawable.
4. transfer_pixels (gdouble *src1, gdouble *src2, guchar *dest, gint jump, gint bytes, gint width) -
It is a gaussian blur helper function which transfer the pixels from source pointed by src1 and src2 to the destination 'dest'.
If there are more than two bytes per pixel( if RGB ) then it computes the luminance value corresponding to the RGB triplet. The lightness value is computed as -
L = (max(R, G, B) + min (R, G, B)) / 2
5. compute_ramp (guchar *dest1, guchar *dest2, gint length, gdouble pct_black) -
It computes the ratio between the two destination images( blur, mask ) and it calculates the number of pixels 'count' for which this difference is < 1.
Now it calcultes the average such that avg = ( hist[0] + hist[1] + hist[2] + .............+ hist[n] ) /count where 'n' is the index where avg > pct_black and at that point where we reach the desired pct_black the function returns the ramp as ( 1 - n/100 )
Photocopy -
header file - libgimp/gimp.h makes all basic plugin elements available to us.
Structures defined-
1. PhotocopyVals - holds parameters - mask_radius,sharpness,threshold,pct_black,pct_white
mask_radius - controls the size of the pixel neighbourhood over which the average intensity is computed and then compared to each pixel in the neighborhood to decide whether or not to darken it. Large values result in very thick black areas bordering the regions of white and much less detail for black areas. Small values result in less toner overall and more details everywhere.
sharpness - defines photocopy sharpness.
threshold - relative intensity difference which will result in darkening
pct_black - decides the amount of black color added to the image
pct_white - white pixel percentage.
Local Variables -
1. pvals - storing default values for the parameters of the structure PhotocopyVals.
2. GimpPlugInInfo PLUG_IN_INFO - Contains four pointers to different functions which are called during plugin execution.
a)init - optional(can have null value) and is called as GIMP starts up. It can be called if we want to register some procedure conditionally on some files prescence.
b)quit - also optional( can have null value ) and is called when GIMP is going to close.
c)query - called when the plugin comes into existence or every time when it is modified.
d)run - it is the plugin processing function which receives the plugin name, input parameters, number of return values, pointer to output parameters.
MAIN() - it is a macro defined for calling the initialisation and calling appropriate functions that our plugin needs during its life time.
Functions -
1. query() - defines the input arguments
Structure GimpParamDef contains - type, name and description.
It registers the function in the path specified as here under "<Image>/Filters/Artistic"
2. photocopy_dialog (GimpDrawable *drawable) -
opens a dialog box for the user for specifying the basic input parameters. This also function holds the basic layout informaion for the dialog box. It clearly mentions the existence of 4 scale bars ( mask radius, sharpness, percent white, percent black ), preview window and ok button. User can change the value of parameters and have a preview for every changed argument.The widget does not gets destroyed until the ok button( signal - GTK_RESPONSE_OK ) or cancel button is pressed and the final parameters are then saved.
3. photocopy(GimpDrawable *drawable,GimpPreview *preview) -
Every variable of the GimpDrawable struct has a drawable id, width, height,bytes per pixel,number of tile rows, number of tile columns, normal tiles and shadow tiles. Here we check if the drawable has an alpha channel associated with it. Alpha channel can be there with the layer types such as RGB, GRAYSCALE and it defines the amount of opacity of the layer.
Initialise 6 memory locations val_p1,val_p2,val_m1,val_m2,dest1(blur radius),dest2(mask radius). Initialise the pixel region pointed by 'src_rgn', new region being attached to drawable region,(0,0) as initial coordinates, width as drawable->width, height as drawable->height.
It desaturates the image, computes transfer and then calculates the standard deviations - sharpness and mask radius. Now calculate the value of needed constants from the 'Gaussian-blur helper function' - find_constants.
Start the analysis of image by taking vertical strips into consideration begining from column 0 till width. gimp_pixel_rgn_get_col(col+x1, y1 ) gets all pixels in a column from (col+x1,y1) to (col+x1, y1+height-1 ) and fills the buffer src with it.sp_p1 holds the value for first pixel and sp_m1 holds the value for the last pixel and with these values and the values calculated by the find_constants functions we calculate every pixel along a column and then use the user defined function 'transfer_pixels' to transfer these pixel to the destination. gimp_progress_update() updates the progress bar for the current plugin.
Similary we analyse it now by taking horizontal strips begining from row 0 to row height.Initialise 4 memory locations for holding the values, 2 for the source buffer( src1, src2 ).Initialise the initial pixels i.e the starting row pixel 0 and width-1 and with the help of the values calculated from the gaussian function calculate every pixel along a row and use transfer_pixels() function to transfer these pixels to the destination.
Thus we first move column-wise and then row-wise to analyse every pixel.
Compute the ramp values - ramp_up and ramp_down.ramp_up sets the pct_black whereas ramp_down sets the pct_white of the pixels.
Initialise and register the pixel region . dest1 deals with the calculations for blur radius and dest2 deals with the calculations for the mask radius.For every pixel calculate the diff as the ratio of the blur intensity to that of the average intensity.
If diff < threshold and if ramp_down != 0 then mult = (ramp_down - MIN (ramp_down, (pvals.threshold - diff))) / ramp_down. The lightness for every pixel calculated as blur_ptr[col]*mult is CLAMPED between 0 to 255.
Else if diff > threshold and ramp_up ! = 0 then mult = MIN (ramp_up, (diff - pvals.threshold)) / ramp_up. The lightness for every pixel calculated as 255 - (1.0 - mult) * (255 - blur_ptr[col]) CLAMPED between 0 to 255.
Check If number of bytes per pixel is less than 3(grayscale / grayscale+alpha) or bpp > 3 ( RBG/RGB+alpha ) and accordingly set the destnation pixel.
And after it we merge the shadow tile and update the drawable.And free the unused buffers.
4. transfer_pixels (gdouble *src1, gdouble *src2, guchar *dest, gint jump, gint bytes, gint width) -
It is a gaussian blur helper function which transfer the pixels from source pointed by src1 and src2 to the destination 'dest'.
5. compute_ramp (guchar *dest1, guchar *dest2, gint length, gdouble pct_black) -
It computes the ratio between the two destination images( blur, mask ) and checks if the diff is under_threshold or not.It calculates the number of pixels 'count' for which this difference is < threshold ,diff > threshold && diff < 2
Now it calculates the average such that avg = ( hist[0] + hist[1] + hist[2] + .............+ hist[n] ) /count where 'n' is the index where avg > pct, now check if diff was under_threshold then return (pvals.threshold - (gdouble) n / 1000.0) else return ((gdouble) n / 1000.0 - pvals.threshold)
This was what I understood to the best of my knowledge and looking forward for suggestions to improve it or do some other task.
Besides this I will submit the sample implementation of new GEGL OP as a patch against the gegl main branch by today evening.
Thanking you in advance
--
Shivani Maheshwari
Under Graduation( BTech.)
Indian Institute of Information Technology,
Allahabad (Amethi Campus)
India
_______________________________________________ Gimp-developer mailing list Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
