Re: [ft] Questions using FT_RENDER_MODE_MONO

[kevinkreiser]

Forgot to mention that the out put of this is a single channel image not a 4
channel image like you were looking for, easy enough to modify it to do that
though. I'll let that exercise for you.


kevinkreiser wrote:
> 
> This is how I do it:
> 
> vector<unsigned char> getImage(const FT_Bitmap& bitmap)
> {
>       //make some space, plus a little just in case we are doing 1bit
> image
>       vector<unsigned char> image;
>       image.resize(bitmap.width * bitmap.height + 8, 0);
>       //copy it in
>       if(image.size() > 0)
>       {
>          //for each row in the image
>          for(int r = 0; r < bitmap.rows; r++)
>          {
>             //where does this row go in our texture
>             int index = r * width;
> 
>             //if its 1bit
>             if(bitmap.pixel_mode == FT_PIXEL_MODE_MONO)
>             {
>                //for each byte
>                for(int c = 0, byteIndex = r * bitmap.pitch; c <
> bitmap.width; c+=8, byteIndex++)
>                {
>                   //unroll this byte into its bits, note here we can write
> some bits that we dont actually use
>                   //if the width doesn't line up to exact byte boundaries,
> might only happen on last pix
>                   image[index++] = ((bitmap.buffer[byteIndex] & 128) ==
> 128   ? 255 : 0);
>                   image[index++] = ((bitmap.buffer[byteIndex] & 64)  == 64   
> ? 255 : 0);
>                   image[index++] = ((bitmap.buffer[byteIndex] & 32)  == 32   
> ? 255 : 0);
>                   image[index++] = ((bitmap.buffer[byteIndex] & 16)  == 16   
> ? 255 : 0);
>                   image[index++] = ((bitmap.buffer[byteIndex] & 8)   == 8    
> ? 255 : 0);
>                   image[index++] = ((bitmap.buffer[byteIndex] & 4)   == 4    
> ? 255 : 0);
>                   image[index++] = ((bitmap.buffer[byteIndex] & 2)   == 2    
> ? 255 : 0);
>                   image[index++] = ((bitmap.buffer[byteIndex] & 1)   == 1    
> ? 255 : 0);
>                }
>             }//grayscale 8bit
>             else if(bitmap.pixel_mode == FT_PIXEL_MODE_GRAY)
>             {
>                //copy the whole row of pixels
>                memcpy((void*)&image[index], (void*)&bitmap.buffer[r *
> bitmap.width], bitmap.width);
>             }
>             else
>             {
>                //TODO: throw exception
>                //for now silently fail...
>             }
>          }
>          //incase we had to take more than we needed trim the image back
> to its real size
>          image.resize(size, 0);
>          //give it back
>          return image;
> }
> 
> 
> Graham Hemingway wrote:
>> 
>> Hello,   I am relatively new to FreeType, and first I want to say thank
>> you
>> to the developers.  Well, my question is about the format of the bitmap
>> buffer returned by using FT_RENDER_MODE_MONO.  I want to get bitmaps that
>> are not anti-aliased and my end target is OpenGL textures that use
>> 32-bits
>> per pixel (8 per channel RGBA).  So I need to do the conversion from the
>> 1-bit per pixel output.  What I would like is for all four components of
>> the
>> texture (unsigned bytes) to be either 0 or 255 based on the glyph bitmap.
>>  Below is some code that I tried but it only rendered garbage.  Any
>> suggestions on how to go about this?
>> 
>> //Allocate memory for the texture data (four component)
>> GLubyte *data = new GLubyte[4 * slot->bitmap.width * slot->bitmap.rows];
>> 
>> //Set color to white and alpha to bitmap value
>> unsigned int bmIndex = 0, dataIndex = 0, byteIndex, bitOffset;
>> unsigned char byte;
>> for(int j=0; j < slot->bitmap.rows; j++) {
>> for(int i=0; i < slot->bitmap.width; i++){
>> 
>> //Get the byte index and bit offset
>>                         byteIndex = bmIndex / 8;
>>                         bitOffset = bmIndex % 8;
>> 
>>                         //Get the byte
>> byte = slot->bitmap.buffer[byteIndex];
>> 
>>                         //Rotate, AND, and multiply to get 0 or 255 value
>>                         byte = ((byte >> bitOffset) & 1) * 255;
>> 
>>                         //Set all four components of the GL texture
>> data[dataIndex++] = byte;
>> data[dataIndex++] = byte;
>> data[dataIndex++] = byte;
>> data[dataIndex++] = byte;
>>                         //Increment bmIndex
>>                         bmIndex++;
>> }
>> }
>> 
>> Thanks,
>>     Graham
>> 
>> _______________________________________________
>> Freetype mailing list
>> address@hidden
>> http://lists.nongnu.org/mailman/listinfo/freetype
>> 
>> 
> 
> 

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