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cb_val:= flat(Cb, xmb, ymb) - 128;
cr_val:= flat(Cr, xmb, ymb) - 128;
Out_Pixel_8(
br => U8(Clip((y_val + 359 * cr_val + 128) / 256)),
bg => U8(Clip((y_val - 88 * cb_val - 183 * cr_val + 128) / 256)),
bb => U8(Clip((y_val + 454 * cb_val + 128) / 256))
);
when Y_Grey =>
y_val_8:= U8(flat(Y, xmb, ymb));
Out_Pixel_8(y_val_8, y_val_8, y_val_8);
when CMYK =>
-- !! find a working conversion formula.
-- perhaps it is more complicated (APP_2
-- color profile must be used ?)
c_val:= flat(Y, xmb, ymb);
m_val:= flat(Cb, xmb, ymb);
y_val:= flat(Cr, xmb, ymb);
w_val:= flat(I, xmb, ymb)-255;
Out_Pixel_8(
br => U8(255-Clip(c_val+w_val)),
bg => U8(255-Clip(m_val+w_val)),
bb => U8(255-Clip(y_val+w_val))
);
end case;
end loop;
end loop;
end Color_transformation_and_output;
--
procedure Ct_YCbCr is new Color_transformation_and_output(YCbCr);
procedure Ct_Y_Grey is new Color_transformation_and_output(Y_Grey);
procedure Ct_CMYK is new Color_transformation_and_output(CMYK);
blk_idx: Integer;
upsx, upsy: Natural;
begin
-- Step 4 happens here: Upsampling
for c in Component loop
if image.JPEG_stuff.components(c) then
upsx:= info_A(c).up_factor_x;
upsy:= info_A(c).up_factor_y;
for x in reverse 1..info_A(c).samples_hor loop
for y in reverse 1..info_A(c).samples_ver loop
-- We are at the 8x8 block level
blk_idx:= 63;
for y8 in reverse 0..7 loop
for x8 in reverse 0..7 loop
declare
val: constant Integer:= m(c,x,y)(blk_idx);
big_pixel_x: constant Natural:= upsx * (x8 + 8*(x-1));
big_pixel_y: constant Natural:= upsy * (y8 + 8*(y-1));
begin
-- Repeat pixels for component c, sample (x,y),
-- position (x8,y8).
for rx in reverse 0..upsx-1 loop
for ry in reverse 0..upsy-1 loop
flat(c, rx + big_pixel_x, ry + big_pixel_y):= val;
end loop;
end loop;
Function Definition: procedure Read_SOS is
Function Body: components, b, id_base: U8;
compo: Component:= Component'First;
mbx, mby: Natural:= 0;
mbsizex, mbsizey, mbwidth, mbheight: Natural;
rstcount: Natural:= image.JPEG_stuff.restart_interval;
nextrst: U16:= 0;
w: U16;
start_spectral_selection,
end_spectral_selection,
successive_approximation: U8;
begin
Get_Byte(image.buffer, components);
if some_trace then
Put_Line(
"Start of Scan (SOS), with" & U8'Image(components) & " components"
);
end if;
if image.subformat_id /= Natural(components) then
Raise_Exception(
error_in_image_data'Identity,
"JPEG: components mismatch in Scan segment"
);
end if;
id_base := 1;
for i in 1..components loop
Get_Byte(image.buffer, b);
if b = 0 then
-- Workaround for bugged encoder (see above)
id_base := 0;
end if;
if b - id_base > Component'Pos(Component'Last) then
Raise_Exception(error_in_image_data'Identity, "Scan: invalid ID: " & U8'Image(b));
end if;
compo:= Component'Val(b - id_base);
if not image.JPEG_stuff.components(compo) then
Raise_Exception(
error_in_image_data'Identity,
"JPEG: component " & Component'Image(compo) &
" has not been defined in the header (SOF) segment"
);