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DrawingTidbits.cpp：源码内容
							/*****************************************************************************
 * DrawingTidbits.cpp
 *****************************************************************************
 * Copyright (C) 2001 the VideoLAN team
 * $Id: 362933f5efd189ed8670a19d94c99d1d19e3e5a2 $
 *
 * Authors: Tony Castley <tcastley@mail.powerup.com.au>
 *          Stephan Aßmus <stippi@yellowbites.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/
#include <math.h>
#include <Bitmap.h>
#include <Debug.h>
#include <Screen.h>
#include "DrawingTidbits.h"
// ShiftComponent
inline uchar
ShiftComponent(uchar component, float percent)
{
    // change the color by <percent>, make sure we aren't rounding
    // off significant bits
    if (percent >= 1)
        return (uchar)(component * (2 - percent));
    else
        return (uchar)(255 - percent * (255 - component));
}
// ShiftColor
rgb_color
ShiftColor(rgb_color color, float percent)
{
    rgb_color result = {
        ShiftComponent(color.red, percent),
        ShiftComponent(color.green, percent),
        ShiftComponent(color.blue, percent),
        0
    };
    
    return result;
}
// CompareColors
static bool
CompareColors(const rgb_color a, const rgb_color b)
{
    return a.red == b.red
        && a.green == b.green
        && a.blue == b.blue
        && a.alpha == b.alpha;
}
// ==
bool
operator==(const rgb_color &a, const rgb_color &b)
{
    return CompareColors(a, b);
}
// !=
bool
operator!=(const rgb_color &a, const rgb_color &b)
{
    return !CompareColors(a, b);
}
// ReplaceColor
void
ReplaceColor(BBitmap *bitmap, rgb_color from, rgb_color to)
{
    ASSERT(bitmap->ColorSpace() == B_COLOR_8_BIT); // other color spaces not implemented yet
    
    BScreen screen(B_MAIN_SCREEN_ID);
    uint32 fromIndex = screen.IndexForColor(from);
    uint32 toIndex = screen.IndexForColor(to);
    
    uchar *bits = (uchar *)bitmap->Bits();
    int32 bitsLength = bitmap->BitsLength();    
    for (int32 index = 0; index < bitsLength; index++)
        if (bits[index] == fromIndex)
            bits[index] = toIndex;
}
// ReplaceTransparentColor
void
ReplaceTransparentColor(BBitmap *bitmap, rgb_color with)
{
    ASSERT(bitmap->ColorSpace() == B_COLOR_8_BIT); // other color spaces not implemented yet
    
    BScreen screen(B_MAIN_SCREEN_ID);
    uint32 withIndex = screen.IndexForColor(with);
    
    uchar *bits = (uchar *)bitmap->Bits();
    int32 bitsLength = bitmap->BitsLength();    
    for (int32 index = 0; index < bitsLength; index++)
        if (bits[index] == B_TRANSPARENT_8_BIT)
            bits[index] = withIndex;
}
// ycrcb_to_rgb
inline void
ycbcr_to_rgb( uint8 y, uint8 cb, uint8 cr,
              uint8& r, uint8& g, uint8& b)
{
    r = (uint8)max_c( 0, min_c( 255, 1.164 * ( y - 16 ) + 1.596 * ( cr - 128 ) ) );
    g = (uint8)max_c( 0, min_c( 255, 1.164 * ( y - 16 ) - 0.813 * ( cr - 128 )
                                - 0.391 * ( cb - 128 ) ) );
    b = (uint8)max_c( 0, min_c( 255, 1.164 * ( y - 16 ) + 2.018 * ( cb - 128 ) ) );
}
// this function will not produce visually pleasing results!
// we'd have to convert to Lab colorspace, do the mixing
// and convert back to RGB - in an ideal world...
//
// mix_colors
inline void
mix_colors( uint8 ra, uint8 ga, uint8 ba,
            uint8 rb, uint8 gb, uint8 bb,
            uint8& r, uint8& g, uint8& b, float mixLevel )
{
    float mixA = ( 1.0 - mixLevel );
    float mixB = mixLevel;
    r = (uint8)(mixA * ra + mixB * rb);
    g = (uint8)(mixA * ga + mixB * gb);
    b = (uint8)(mixA * ba + mixB * bb);
}
// the algorithm used is probably pretty slow, but it should be easy
// to understand what's going on...
//
// scale_bitmap
status_t
scale_bitmap( BBitmap* bitmap, uint32 fromWidth, uint32 fromHeight )
{
    status_t status = B_BAD_VALUE;
    
    if ( bitmap && bitmap->IsValid()
         && ( bitmap->ColorSpace() == B_RGB32 || bitmap->ColorSpace() == B_RGBA32 ) )
    {
        status = B_MISMATCHED_VALUES;
        // we only support upscaling as of now
        uint32 destWidth = bitmap->Bounds().IntegerWidth() + 1;
        uint32 destHeight = bitmap->Bounds().IntegerHeight() + 1;
        if ( fromWidth <= destWidth && fromHeight <= destHeight )
        {
            status = B_OK;
            uint32 bpr = bitmap->BytesPerRow();
            if ( fromWidth < destWidth )
            {
                // scale horizontally
                uint8* src = (uint8*)bitmap->Bits();
                uint8* p = new uint8[fromWidth * 4];    // temp buffer
                for ( uint32 y = 0; y < fromHeight; y++ )
                {
                    // copy valid pixels into temp buffer
                    memcpy( p, src, fromWidth * 4 );
                    for ( uint32 x = 0; x < destWidth; x++ )
                    {
                        // mix colors of left and right pixels and write it back
                        // into the bitmap
                        float xPos = ( (float)x / (float)destWidth ) * (float)fromWidth;
                        uint32 leftIndex = (uint32)floorf( xPos ) * 4;
                        uint32 rightIndex = (uint32)ceilf( xPos ) * 4;
                        rgb_color left;
                        left.red = p[leftIndex + 2];
                        left.green = p[leftIndex + 1];
                        left.blue = p[leftIndex + 0];
                        rgb_color right;
                        right.red = p[rightIndex + 2];
                        right.green = p[rightIndex + 1];
                        right.blue = p[rightIndex + 0];
                        rgb_color mix;
                        mix_colors( left.red, left.green, left.blue,
                                    right.red, right.green, right.blue,
                                    mix.red, mix.green, mix.blue, xPos - floorf( xPos ) );
                        uint32 destIndex = x * 4;
                        src[destIndex + 2] = mix.red;
                        src[destIndex + 1] = mix.green;
                        src[destIndex + 0] = mix.blue;
                    }
                    src += bpr;
                }
                delete[] p;
            }
            if ( fromHeight < destHeight )
            {
                // scale vertically
                uint8* src = (uint8*)bitmap->Bits();
                uint8* p = new uint8[fromHeight * 3];    // temp buffer
                for ( uint32 x = 0; x < destWidth; x++ )
                {
                    // copy valid pixels into temp buffer
                    for ( uint32 y = 0; y < fromHeight; y++ )
                    {
                        uint32 destIndex = y * 3;
                        uint32 srcIndex = x * 4 + y * bpr;
                        p[destIndex + 0] = src[srcIndex + 0];
                        p[destIndex + 1] = src[srcIndex + 1];
                        p[destIndex + 2] = src[srcIndex + 2];
                    }
                    // do the scaling
                    for ( uint32 y = 0; y < destHeight; y++ )
                    {
                        // mix colors of upper and lower pixels and write it back
                        // into the bitmap
                        float yPos = ( (float)y / (float)destHeight ) * (float)fromHeight;
                        uint32 upperIndex = (uint32)floorf( yPos ) * 3;
                        uint32 lowerIndex = (uint32)ceilf( yPos ) * 3;
                        rgb_color upper;
                        upper.red = p[upperIndex + 2];
                        upper.green = p[upperIndex + 1];
                        upper.blue = p[upperIndex + 0];
                        rgb_color lower;
                        lower.red = p[lowerIndex + 2];
                        lower.green = p[lowerIndex + 1];
                        lower.blue = p[lowerIndex + 0];
                        rgb_color mix;
                        mix_colors( upper.red, upper.green, upper.blue,
                                    lower.red, lower.green, lower.blue,
                                    mix.red, mix.green, mix.blue, yPos - floorf( yPos ) );
                        uint32 destIndex = x * 4 + y * bpr;
                        src[destIndex + 2] = mix.red;
                        src[destIndex + 1] = mix.green;
                        src[destIndex + 0] = mix.blue;
                    }
                }
                delete[] p;
            }
        }
    }
    return status;
}
// convert_bitmap
status_t
convert_bitmap( BBitmap* inBitmap, BBitmap* outBitmap )
{
    status_t status = B_BAD_VALUE;
    // see that we got valid bitmaps
    if ( inBitmap && inBitmap->IsValid()
         && outBitmap && outBitmap->IsValid() )
    {
        status = B_MISMATCHED_VALUES;
        // see that bitmaps are compatible and that we support the conversion
        if ( inBitmap->Bounds().Width() <= outBitmap->Bounds().Width()
             && inBitmap->Bounds().Height() <= outBitmap->Bounds().Height()
             && ( outBitmap->ColorSpace() == B_RGB32
                  || outBitmap->ColorSpace() == B_RGBA32) )
        {
            int32 width = inBitmap->Bounds().IntegerWidth() + 1;
            int32 height = inBitmap->Bounds().IntegerHeight() + 1;
            int32 srcBpr = inBitmap->BytesPerRow();
            int32 dstBpr = outBitmap->BytesPerRow();
            uint8* srcBits = (uint8*)inBitmap->Bits();
            uint8* dstBits = (uint8*)outBitmap->Bits();
            switch (inBitmap->ColorSpace())
            {
                case B_YCbCr422:
                    // Y0[7:0]  Cb0[7:0]  Y1[7:0]  Cr0[7:0]
                    // Y2[7:0]  Cb2[7:0]  Y3[7:0]  Cr2[7:0]
                    for ( int32 y = 0; y < height; y++ )
                    {
                        for ( int32 x = 0; x < width; x += 2 )
                        {
                            int32 srcOffset = x * 2;
                            int32 dstOffset = x * 4;
                            ycbcr_to_rgb( srcBits[srcOffset + 0],
                                          srcBits[srcOffset + 1],
                                          srcBits[srcOffset + 3],
                                          dstBits[dstOffset + 2],
                                          dstBits[dstOffset + 1],
                                          dstBits[dstOffset + 0] );
                            ycbcr_to_rgb( srcBits[srcOffset + 2],
                                          srcBits[srcOffset + 1],
                                          srcBits[srcOffset + 3],
                                          dstBits[dstOffset + 6],
                                          dstBits[dstOffset + 5],
                                          dstBits[dstOffset + 4] );
                            // take care of alpha
                            dstBits[x * 4 + 3] = 255;
                            dstBits[x * 4 + 7] = 255;
                        }
                        srcBits += srcBpr;
                        dstBits += dstBpr;
                    }
                    status = B_OK;
                    break;
                case B_YCbCr420:
                    // Non-interlaced only!
                    // Cb0  Y0  Y1  Cb2 Y2  Y3  on even scan lines ...
                    // Cr0  Y0  Y1  Cr2 Y2  Y3  on odd scan lines
                    status = B_ERROR;
                    break;
                case B_YUV422:
                    // U0[7:0]  Y0[7:0]   V0[7:0]  Y1[7:0]
                    // U2[7:0]  Y2[7:0]   V2[7:0]  Y3[7:0]
                    status = B_ERROR;
                    break;
                case B_RGB32:
                case B_RGBA32:
                    memcpy( dstBits, srcBits, inBitmap->BitsLength() );
                    status = B_OK;
                    break;
                case B_RGB16:
                    // G[2:0],B[4:0]  R[4:0],G[5:3]
                    for ( int32 y = 0; y < height; y ++ )
                    {
                        for ( int32 x = 0; x < width; x++ )
                        {
                            int32 srcOffset = x * 2;
                            int32 dstOffset = x * 4;
                            uint8 blue = srcBits[srcOffset + 0] & 0x1f;
                            uint8 green = ( srcBits[srcOffset + 0] >> 5 )
                                          | ( ( srcBits[srcOffset + 1] & 0x07 ) << 3 );
                            uint8 red = srcBits[srcOffset + 1] & 0xf8;
                            // homogeneously scale each component to 8 bit
                            dstBits[dstOffset + 0] = (blue << 3) | (blue >> 2);
                            dstBits[dstOffset + 1] = (green << 2) | (green >> 4);
                            dstBits[dstOffset + 2] = red | (red >> 5);
                        }
                        srcBits += srcBpr;
                        dstBits += dstBpr;
                    }
                    status = B_OK;
                    break;
                default:
                    status = B_MISMATCHED_VALUES;
                    break;
            }
            if ( status == B_OK )
            {
                if ( width < outBitmap->Bounds().IntegerWidth() + 1
                     || height < outBitmap->Bounds().IntegerHeight() + 1 )
                {
                    scale_bitmap( outBitmap, width, height );
                }
            }
        }
    }
    return status;
}
// clip_float
inline uint8
clip_float(float value)
{
    if (value < 0)
        value = 0;
    if (value > 255)
        value = 255;
    return (uint8)value;
}
// dim_bitmap
status_t
dim_bitmap(BBitmap* bitmap, rgb_color center, float dimLevel)
{
    status_t status = B_BAD_VALUE;
    if (bitmap && bitmap->IsValid())
    {
        switch (bitmap->ColorSpace())
        {
            case B_CMAP8:
            {
                BScreen screen(B_MAIN_SCREEN_ID);
                if (screen.IsValid())
                {
                    // iterate over each pixel, get the respective
                    // color from the screen object, find the distance
                    // to the "center" color and shorten the distance
                    // by "dimLevel"
                    int32 length = bitmap->BitsLength();
                    uint8* bits = (uint8*)bitmap->Bits();
                    for (int32 i = 0; i < length; i++)
                    {
                        // preserve transparent pixels
                        if (bits[i] != B_TRANSPARENT_MAGIC_CMAP8)
                        {
                            // get color for this index
                            rgb_color c = screen.ColorForIndex(bits[i]);
                            // red
                            float dist = (c.red - center.red) * dimLevel;
                            c.red = clip_float(center.red + dist);
                            // green
                            dist = (c.green - center.green) * dimLevel;
                            c.green = clip_float(center.green + dist);
                            // blue
                            dist = (c.blue - center.blue) * dimLevel;
                            c.blue = clip_float(center.blue + dist);
                            // write correct index of the dimmed color
                            // back into bitmap (and hope the match is close...)
                            bits[i] = screen.IndexForColor(c);
                        }
                    }
                    status = B_OK;
                }
                break;
            }
            case B_RGB32:
            case B_RGBA32:
            {
                // iterate over each color component, find the distance
                // to the "center" color and shorten the distance
                // by "dimLevel"
                uint8* bits = (uint8*)bitmap->Bits();
                int32 bpr = bitmap->BytesPerRow();
                int32 pixels = bitmap->Bounds().IntegerWidth() + 1;
                int32 lines = bitmap->Bounds().IntegerHeight() + 1;
                // iterate over color components
                for (int32 y = 0; y < lines; y++) {
                    for (int32 x = 0; x < pixels; x++) {
                        int32 offset = 4 * x; // four bytes per pixel
                        // blue
                        float dist = (bits[offset + 0] - center.blue) * dimLevel;
                        bits[offset + 0] = clip_float(center.blue + dist);
                        // green
                        dist = (bits[offset + 1] - center.green) * dimLevel;
                        bits[offset + 1] = clip_float(center.green + dist);
                        // red
                        dist = (bits[offset + 2] - center.red) * dimLevel;
                        bits[offset + 2] = clip_float(center.red + dist);
                        // ignore alpha channel
                    }
                    // next line
                    bits += bpr;
                }
                status = B_OK;
                break;
            }
            default:
                status = B_ERROR;
                break;
        }
    }
    return status;
}
// dimmed_color_cmap8
rgb_color
dimmed_color_cmap8(rgb_color color, rgb_color center, float dimLevel)
{
    BScreen screen(B_MAIN_SCREEN_ID);
    if (screen.IsValid())
    {
        // red
        float dist = (color.red - center.red) * dimLevel;
        color.red = clip_float(center.red + dist);
        // green
        dist = (color.green - center.green) * dimLevel;
        color.green = clip_float(center.green + dist);
        // blue
        dist = (color.blue - center.blue) * dimLevel;
        color.blue = clip_float(center.blue + dist);
        // get color index for dimmed color
        int32 index = screen.IndexForColor(color);
        // put color at index (closest match in palette
        // to dimmed result) into returned color
        color = screen.ColorForIndex(index);
    }
    return color;
}

						