Add initial prototype.

2022-07-31 17:34:54 +10:00
commit 54a53b2ac0
1421 changed files with 358874 additions and 0 deletions
--- a/3-mid/opengl/private/gid/gid-decoding_png.ads
+++ b/3-mid/opengl/private/gid/gid-decoding_png.ads
@@ -0,0 +1,77 @@
+private package GID.Decoding_PNG is
+
+  type PNG_Chunk_tag is (
+    --
+    -- Critical chunks
+    --
+    IHDR, --    must be the first chunk; it contains the header.
+    PLTE, --    contains the palette; list of colors.
+    IDAT, --    contains the image, which may be split among multiple IDAT chunks.
+    IEND, --    marks the image end.
+    --
+    -- Ancillary chunks
+    --
+    bKGD, --    gives the default background color.
+    cHRM, --    gives the chromaticity coordinates of the display primaries and white point.
+    gAMA, --    specifies gamma.
+    hIST, --    can store the histogram, or total amount of each color in the image.
+    iCCP, --    is an ICC color profile.
+    iTXt, --    contains UTF-8 text, compressed or not, with an optional language tag.
+    pHYs, --    holds the intended pixel size and/or aspect ratio of the image.
+    sBIT, --    (significant bits) indicates the color-accuracy of the source data.
+    sPLT, --    suggests a palette to use if the full range of colors is unavailable.
+    sRGB, --    indicates that the standard sRGB color space is used.
+    tEXt, --    can store text that can be represented in ISO/IEC 8859-1.
+    tIME, --    stores the time that the image was last changed.
+    tRNS, --    contains transparency information.
+    zTXt, --    contains compressed text with the same limits as tEXt.
+    --
+    -- Public extentions
+    -- PNG Extensions and Register of Public Chunks and Keywords
+    --
+    oFFs, -- image offset from frame or page origin
+    pCAL, -- physical calibration of pixel values
+    sCAL, -- physical scale of image subject
+    sTER, -- stereographic subimage layout
+    gIFg, -- GIF Graphic Control Extension
+    gIFx, -- GIF Application Extension
+    fRAc, -- fractal image parameters
+    --
+    -- Private chunks (not defined in the ISO standard)
+    --
+    vpAg, --    used in ImageMagick to store "virtual page" size
+    spAL,
+    prVW,
+    cmOD,
+    cmPP,
+    cpIp,
+    mkBF,
+    mkBS,
+    mkBT,
+    mkTS,
+    pcLb
+  );
+
+  type Chunk_head is record
+    length: U32;
+    kind  : PNG_Chunk_tag;
+  end record;
+
+  procedure Read( image: in out image_descriptor; ch: out Chunk_head);
+
+  --------------------
+  -- Image decoding --
+  --------------------
+
+  generic
+    type Primary_color_range is mod <>;
+    with procedure Set_X_Y (x, y: Natural);
+    with procedure Put_Pixel (
+      red, green, blue : Primary_color_range;
+      alpha            : Primary_color_range
+    );
+    with procedure Feedback (percents: Natural);
+  --
+  procedure Load (image: in out Image_descriptor);
+
+end GID.Decoding_PNG;