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436 lines
9.8 KiB
C
436 lines
9.8 KiB
C
/*
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Jonathan Dummer
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image helper functions
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MIT license
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*/
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#include "image_helper.h"
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#include <stdlib.h>
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#include <math.h>
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/* Upscaling the image uses simple bilinear interpolation */
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int
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up_scale_image
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(
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const unsigned char* const orig,
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int width, int height, int channels,
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unsigned char* resampled,
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int resampled_width, int resampled_height
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)
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{
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float dx, dy;
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int x, y, c;
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/* error(s) check */
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if ( (width < 1) || (height < 1) ||
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(resampled_width < 2) || (resampled_height < 2) ||
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(channels < 1) ||
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(NULL == orig) || (NULL == resampled) )
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{
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/* signify badness */
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return 0;
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}
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/*
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for each given pixel in the new map, find the exact location
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from the original map which would contribute to this guy
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*/
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dx = (width - 1.0f) / (resampled_width - 1.0f);
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dy = (height - 1.0f) / (resampled_height - 1.0f);
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for ( y = 0; y < resampled_height; ++y )
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{
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/* find the base y index and fractional offset from that */
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float sampley = y * dy;
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int inty = (int)sampley;
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/* if( inty < 0 ) { inty = 0; } else */
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if( inty > height - 2 ) { inty = height - 2; }
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sampley -= inty;
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for ( x = 0; x < resampled_width; ++x )
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{
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float samplex = x * dx;
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int intx = (int)samplex;
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int base_index;
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/* find the base x index and fractional offset from that */
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/* if( intx < 0 ) { intx = 0; } else */
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if( intx > width - 2 ) { intx = width - 2; }
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samplex -= intx;
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/* base index into the original image */
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base_index = (inty * width + intx) * channels;
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for ( c = 0; c < channels; ++c )
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{
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/* do the sampling */
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float value = 0.5f;
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value += orig[base_index]
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*(1.0f-samplex)*(1.0f-sampley);
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value += orig[base_index+channels]
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*(samplex)*(1.0f-sampley);
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value += orig[base_index+width*channels]
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*(1.0f-samplex)*(sampley);
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value += orig[base_index+width*channels+channels]
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*(samplex)*(sampley);
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/* move to the next channel */
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++base_index;
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/* save the new value */
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resampled[y*resampled_width*channels+x*channels+c] =
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(unsigned char)(value);
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}
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}
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}
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/* done */
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return 1;
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}
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int
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mipmap_image
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(
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const unsigned char* const orig,
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int width, int height, int channels,
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unsigned char* resampled,
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int block_size_x, int block_size_y
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)
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{
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int mip_width, mip_height;
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int i, j, c;
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/* error check */
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if( (width < 1) || (height < 1) ||
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(channels < 1) || (orig == NULL) ||
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(resampled == NULL) ||
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(block_size_x < 1) || (block_size_y < 1) )
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{
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/* nothing to do */
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return 0;
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}
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mip_width = width / block_size_x;
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mip_height = height / block_size_y;
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if( mip_width < 1 )
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{
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mip_width = 1;
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}
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if( mip_height < 1 )
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{
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mip_height = 1;
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}
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for( j = 0; j < mip_height; ++j )
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{
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for( i = 0; i < mip_width; ++i )
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{
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for( c = 0; c < channels; ++c )
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{
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const int index = (j*block_size_y)*width*channels + (i*block_size_x)*channels + c;
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int sum_value;
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int u,v;
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int u_block = block_size_x;
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int v_block = block_size_y;
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int block_area;
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/* do a bit of checking so we don't over-run the boundaries
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(necessary for non-square textures!) */
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if( block_size_x * (i+1) > width )
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{
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u_block = width - i*block_size_y;
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}
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if( block_size_y * (j+1) > height )
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{
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v_block = height - j*block_size_y;
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}
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block_area = u_block*v_block;
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/* for this pixel, see what the average
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of all the values in the block are.
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note: start the sum at the rounding value, not at 0 */
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sum_value = block_area >> 1;
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for( v = 0; v < v_block; ++v )
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for( u = 0; u < u_block; ++u )
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{
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sum_value += orig[index + v*width*channels + u*channels];
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}
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resampled[j*mip_width*channels + i*channels + c] = sum_value / block_area;
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}
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}
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}
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return 1;
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}
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int
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scale_image_RGB_to_NTSC_safe
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(
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unsigned char* orig,
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int width, int height, int channels
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)
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{
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const float scale_lo = 16.0f - 0.499f;
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const float scale_hi = 235.0f + 0.499f;
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int i, j;
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int nc = channels;
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unsigned char scale_LUT[256];
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/* error check */
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if( (width < 1) || (height < 1) ||
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(channels < 1) || (orig == NULL) )
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{
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/* nothing to do */
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return 0;
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}
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/* set up the scaling Look Up Table */
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for( i = 0; i < 256; ++i )
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{
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scale_LUT[i] = (unsigned char)((scale_hi - scale_lo) * i / 255.0f + scale_lo);
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}
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/* for channels = 2 or 4, ignore the alpha component */
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nc -= 1 - (channels & 1);
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/* OK, go through the image and scale any non-alpha components */
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for( i = 0; i < width*height*channels; i += channels )
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{
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for( j = 0; j < nc; ++j )
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{
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orig[i+j] = scale_LUT[orig[i+j]];
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}
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}
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return 1;
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}
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unsigned char clamp_byte( int x ) { return ( (x) < 0 ? (0) : ( (x) > 255 ? 255 : (x) ) ); }
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/*
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This function takes the RGB components of the image
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and converts them into YCoCg. 3 components will be
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re-ordered to CoYCg (for optimum DXT1 compression),
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while 4 components will be ordered CoCgAY (for DXT5
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compression).
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*/
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int
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convert_RGB_to_YCoCg
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(
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unsigned char* orig,
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int width, int height, int channels
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)
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{
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int i;
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/* error check */
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if( (width < 1) || (height < 1) ||
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(channels < 3) || (channels > 4) ||
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(orig == NULL) )
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{
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/* nothing to do */
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return -1;
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}
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/* do the conversion */
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if( channels == 3 )
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{
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for( i = 0; i < width*height*3; i += 3 )
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{
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int r = orig[i+0];
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int g = (orig[i+1] + 1) >> 1;
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int b = orig[i+2];
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int tmp = (2 + r + b) >> 2;
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/* Co */
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orig[i+0] = clamp_byte( 128 + ((r - b + 1) >> 1) );
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/* Y */
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orig[i+1] = clamp_byte( g + tmp );
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/* Cg */
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orig[i+2] = clamp_byte( 128 + g - tmp );
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}
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} else
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{
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for( i = 0; i < width*height*4; i += 4 )
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{
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int r = orig[i+0];
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int g = (orig[i+1] + 1) >> 1;
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int b = orig[i+2];
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unsigned char a = orig[i+3];
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int tmp = (2 + r + b) >> 2;
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/* Co */
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orig[i+0] = clamp_byte( 128 + ((r - b + 1) >> 1) );
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/* Cg */
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orig[i+1] = clamp_byte( 128 + g - tmp );
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/* Alpha */
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orig[i+2] = a;
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/* Y */
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orig[i+3] = clamp_byte( g + tmp );
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}
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}
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/* done */
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return 0;
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}
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/*
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This function takes the YCoCg components of the image
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and converts them into RGB. See above.
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*/
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int
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convert_YCoCg_to_RGB
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(
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unsigned char* orig,
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int width, int height, int channels
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)
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{
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int i;
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/* error check */
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if( (width < 1) || (height < 1) ||
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(channels < 3) || (channels > 4) ||
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(orig == NULL) )
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{
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/* nothing to do */
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return -1;
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}
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/* do the conversion */
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if( channels == 3 )
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{
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for( i = 0; i < width*height*3; i += 3 )
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{
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int co = orig[i+0] - 128;
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int y = orig[i+1];
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int cg = orig[i+2] - 128;
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/* R */
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orig[i+0] = clamp_byte( y + co - cg );
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/* G */
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orig[i+1] = clamp_byte( y + cg );
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/* B */
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orig[i+2] = clamp_byte( y - co - cg );
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}
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} else
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{
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for( i = 0; i < width*height*4; i += 4 )
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{
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int co = orig[i+0] - 128;
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int cg = orig[i+1] - 128;
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unsigned char a = orig[i+2];
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int y = orig[i+3];
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/* R */
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orig[i+0] = clamp_byte( y + co - cg );
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/* G */
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orig[i+1] = clamp_byte( y + cg );
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/* B */
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orig[i+2] = clamp_byte( y - co - cg );
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/* A */
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orig[i+3] = a;
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}
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}
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/* done */
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return 0;
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}
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float
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find_max_RGBE
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(
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unsigned char *image,
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int width, int height
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)
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{
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float max_val = 0.0f;
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unsigned char *img = image;
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int i, j;
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for( i = width * height; i > 0; --i )
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{
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/* float scale = powf( 2.0f, img[3] - 128.0f ) / 255.0f; */
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float scale = ldexp( 1.0f / 255.0f, (int)(img[3]) - 128 );
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for( j = 0; j < 3; ++j )
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{
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if( img[j] * scale > max_val )
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{
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max_val = img[j] * scale;
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}
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}
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/* next pixel */
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img += 4;
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}
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return max_val;
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}
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int
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RGBE_to_RGBdivA
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(
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unsigned char *image,
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int width, int height,
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int rescale_to_max
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)
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{
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/* local variables */
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int i, iv;
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unsigned char *img = image;
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float scale = 1.0f;
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/* error check */
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if( (!image) || (width < 1) || (height < 1) )
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{
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return 0;
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}
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/* convert (note: no negative numbers, but 0.0 is possible) */
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if( rescale_to_max )
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{
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scale = 255.0f / find_max_RGBE( image, width, height );
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}
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for( i = width * height; i > 0; --i )
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{
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/* decode this pixel, and find the max */
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float r,g,b,e, m;
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/* e = scale * powf( 2.0f, img[3] - 128.0f ) / 255.0f; */
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e = scale * ldexp( 1.0f / 255.0f, (int)(img[3]) - 128 );
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r = e * img[0];
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g = e * img[1];
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b = e * img[2];
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m = (r > g) ? r : g;
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m = (b > m) ? b : m;
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/* and encode it into RGBdivA */
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iv = (m != 0.0f) ? (int)(255.0f / m) : 1.0f;
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iv = (iv < 1) ? 1 : iv;
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img[3] = (iv > 255) ? 255 : iv;
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iv = (int)(img[3] * r + 0.5f);
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img[0] = (iv > 255) ? 255 : iv;
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iv = (int)(img[3] * g + 0.5f);
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img[1] = (iv > 255) ? 255 : iv;
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iv = (int)(img[3] * b + 0.5f);
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img[2] = (iv > 255) ? 255 : iv;
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/* and on to the next pixel */
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img += 4;
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}
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return 1;
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}
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int
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RGBE_to_RGBdivA2
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(
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unsigned char *image,
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int width, int height,
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int rescale_to_max
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)
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{
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/* local variables */
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int i, iv;
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unsigned char *img = image;
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float scale = 1.0f;
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/* error check */
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if( (!image) || (width < 1) || (height < 1) )
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{
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return 0;
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}
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/* convert (note: no negative numbers, but 0.0 is possible) */
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if( rescale_to_max )
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{
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scale = 255.0f * 255.0f / find_max_RGBE( image, width, height );
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}
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for( i = width * height; i > 0; --i )
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{
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/* decode this pixel, and find the max */
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float r,g,b,e, m;
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/* e = scale * powf( 2.0f, img[3] - 128.0f ) / 255.0f; */
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e = scale * ldexp( 1.0f / 255.0f, (int)(img[3]) - 128 );
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r = e * img[0];
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g = e * img[1];
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b = e * img[2];
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m = (r > g) ? r : g;
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m = (b > m) ? b : m;
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/* and encode it into RGBdivA */
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iv = (m != 0.0f) ? (int)sqrtf( 255.0f * 255.0f / m ) : 1.0f;
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iv = (iv < 1) ? 1 : iv;
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img[3] = (iv > 255) ? 255 : iv;
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iv = (int)(img[3] * img[3] * r / 255.0f + 0.5f);
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img[0] = (iv > 255) ? 255 : iv;
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iv = (int)(img[3] * img[3] * g / 255.0f + 0.5f);
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img[1] = (iv > 255) ? 255 : iv;
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iv = (int)(img[3] * img[3] * b / 255.0f + 0.5f);
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img[2] = (iv > 255) ? 255 : iv;
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/* and on to the next pixel */
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img += 4;
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}
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return 1;
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}
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