Rename libsprite to librosprite

svn path=/import/jshaw/libsprite/; revision=10012

1 files changed, 702 insertions, 0 deletions

diff --git a/trunk/librosprite.c b/trunk/librosprite.c
new file mode 100644
index 0000000..06e9ea6
--- /dev/null
+++ b/trunk/librosprite.c
@@ -0,0 +1,702 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include "librosprite.h"
+
+/* reads four bytes, 00, 11, 22 and 33, of a byte array b to give 0x33221100 */
+#define BTUINT(b) (b[0] | (b[1] << 8) | (b[2] << 16) | (b[3] << 24))
+
+/* reverse the byte order of a word such that 0xAABBCCDD becomes 0xDDCCBBAA */
+#define BSWAP(word) (((word & (0x000000ff)) << 24) | ((word & 0x0000ff00) << 8) | ((word & 0x00ff0000) >> 8) | ((word & 0xff000000) >> 24))
+
+#define ROSPRITE_OK 0;
+#define ROSPRITE_READ_FAILED 1;
+
+struct rosprite_header {
+	uint32_t width_words; /* width in words */
+	/* height defined in sprite struct */
+	uint32_t first_used_bit; /* old format only (spriteType = 0) */
+	uint32_t last_used_bit;
+	uint32_t image_size; /* bytes */
+	uint32_t mask_size; /* bytes */
+};
+
+struct rosprite_mask_state {
+	uint32_t x;
+	uint32_t y;
+	uint32_t first_used_bit;
+	uint32_t row_max_bit;
+	uint32_t height;
+	uint32_t current_byte_index;
+	uint32_t current_word;
+	uint32_t bpp;
+};
+
+struct rosprite_file_context {
+	FILE* f;
+};
+
+static const struct rosprite_mode oldmodes[] = {
+/*0*/{ .colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*1*/{ .colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 45, .ydpi = 45, .color_model = rosprite_rgb },
+/*2*/{ .colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 22, .ydpi = 45, .color_model = rosprite_rgb },
+
+/*3*/{ .colorbpp = 0, .maskbpp = 0, .mask_width = 0, .xdpi = 0,  .ydpi = 0,  .color_model = rosprite_rgb },
+
+/*4*/{ .colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 45, .ydpi = 45, .color_model = rosprite_rgb },
+/*5*/{ .colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 22, .ydpi = 45, .color_model = rosprite_rgb },
+
+/*6*/{ .colorbpp = 0, .maskbpp = 0, .mask_width = 0, .xdpi = 0,  .ydpi = 0,  .color_model = rosprite_rgb },
+/*7*/{ .colorbpp = 0, .maskbpp = 0, .mask_width = 0, .xdpi = 0,  .ydpi = 0,  .color_model = rosprite_rgb },
+
+/*8*/{ .colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*9*/{ .colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 45, .ydpi = 45, .color_model = rosprite_rgb },
+/*10*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 22, .ydpi = 45, .color_model = rosprite_rgb },
+/*11*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*12*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*13*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 45, .ydpi = 45, .color_model = rosprite_rgb },
+/*14*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*15*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*16*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*17*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*18*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*19*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*20*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*21*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*22*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi =180, .ydpi = 90, .color_model = rosprite_rgb },
+/*23*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*24*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*25*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*26*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*27*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*28*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*29*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*30*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*31*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*32*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 90, .ydpi = 90, .color_model = rosprite_rgb },
+/*33*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*34*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*35*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*36*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*37*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*38*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*39*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*40*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*41*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*42*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*43*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*44*/{.colorbpp = 1, .maskbpp = 1, .mask_width = 1, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*45*/{.colorbpp = 2, .maskbpp = 1, .mask_width = 2, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*46*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 90, .ydpi = 45, .color_model = rosprite_rgb },
+/*47*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 45, .ydpi = 45, .color_model = rosprite_rgb },
+/*48*/{.colorbpp = 4, .maskbpp = 1, .mask_width = 4, .xdpi = 45, .ydpi = 90, .color_model = rosprite_rgb },
+/*49*/{.colorbpp = 8, .maskbpp = 1, .mask_width = 8, .xdpi = 45, .ydpi = 90, .color_model = rosprite_rgb }
+};
+
+/* table for converting a 5bit channel into an 8bit channel (used for 16bpp to 32bpp conversion) */
+static const uint8_t sprite_16bpp_translate[] = {
+	0x00, 0x08, 0x10, 0x18, 0x20, 0x29, 0x31, 0x39,
+	0x41, 0x4a, 0x52, 0x5a, 0x62, 0x6a, 0x73, 0x7b,
+	0x83, 0x8b, 0x94, 0x9c, 0xa4, 0xac, 0xb4, 0xbd,
+	0xc5, 0xcd, 0xd5, 0xde, 0xe6, 0xee, 0xf6, 0xff
+};
+
+/* palettes generated with palette2c.c
+ * which in turn requires sprite_load_palette(FILE* f)
+ * defined in this file
+ */
+static const uint32_t sprite_1bpp_palette[] = { 0xffffffff, 0xff };
+
+static const uint32_t sprite_2bpp_palette[] = { 0xffffffff, 0xbbbbbbff, 0x777777ff, 0xff };
+
+static const uint32_t sprite_4bpp_palette[] = {
+0xffffffff, 0xddddddff, 0xbbbbbbff, 0x999999ff,
+0x777777ff, 0x555555ff, 0x333333ff, 0xff,
+0x4499ff, 0xeeee00ff, 0xcc00ff, 0xdd0000ff,
+0xeeeebbff, 0x558800ff, 0xffbb00ff, 0xbbffff
+};
+
+static const uint32_t sprite_8bpp_palette[] = {
+0xff, 0x111111ff, 0x222222ff, 0x333333ff,
+0x440000ff, 0x551111ff, 0x662222ff, 0x773333ff,
+0x44ff, 0x111155ff, 0x222266ff, 0x333377ff,
+0x440044ff, 0x551155ff, 0x662266ff, 0x773377ff,
+0x880000ff, 0x991111ff, 0xaa2222ff, 0xbb3333ff,
+0xcc0000ff, 0xdd1111ff, 0xee2222ff, 0xff3333ff,
+0x880044ff, 0x991155ff, 0xaa2266ff, 0xbb3377ff,
+0xcc0044ff, 0xdd1155ff, 0xee2266ff, 0xff3377ff,
+0x4400ff, 0x115511ff, 0x226622ff, 0x337733ff,
+0x444400ff, 0x555511ff, 0x666622ff, 0x777733ff,
+0x4444ff, 0x115555ff, 0x226666ff, 0x337777ff,
+0x444444ff, 0x555555ff, 0x666666ff, 0x777777ff,
+0x884400ff, 0x995511ff, 0xaa6622ff, 0xbb7733ff,
+0xcc4400ff, 0xdd5511ff, 0xee6622ff, 0xff7733ff,
+0x884444ff, 0x995555ff, 0xaa6666ff, 0xbb7777ff,
+0xcc4444ff, 0xdd5555ff, 0xee6666ff, 0xff7777ff,
+0x8800ff, 0x119911ff, 0x22aa22ff, 0x33bb33ff,
+0x448800ff, 0x559911ff, 0x66aa22ff, 0x77bb33ff,
+0x8844ff, 0x119955ff, 0x22aa66ff, 0x33bb77ff,
+0x448844ff, 0x559955ff, 0x66aa66ff, 0x77bb77ff,
+0x888800ff, 0x999911ff, 0xaaaa22ff, 0xbbbb33ff,
+0xcc8800ff, 0xdd9911ff, 0xeeaa22ff, 0xffbb33ff,
+0x888844ff, 0x999955ff, 0xaaaa66ff, 0xbbbb77ff,
+0xcc8844ff, 0xdd9955ff, 0xeeaa66ff, 0xffbb77ff,
+0xcc00ff, 0x11dd11ff, 0x22ee22ff, 0x33ff33ff,
+0x44cc00ff, 0x55dd11ff, 0x66ee22ff, 0x77ff33ff,
+0xcc44ff, 0x11dd55ff, 0x22ee66ff, 0x33ff77ff,
+0x44cc44ff, 0x55dd55ff, 0x66ee66ff, 0x77ff77ff,
+0x88cc00ff, 0x99dd11ff, 0xaaee22ff, 0xbbff33ff,
+0xcccc00ff, 0xdddd11ff, 0xeeee22ff, 0xffff33ff,
+0x88cc44ff, 0x99dd55ff, 0xaaee66ff, 0xbbff77ff,
+0xcccc44ff, 0xdddd55ff, 0xeeee66ff, 0xffff77ff,
+0x88ff, 0x111199ff, 0x2222aaff, 0x3333bbff,
+0x440088ff, 0x551199ff, 0x6622aaff, 0x7733bbff,
+0xccff, 0x1111ddff, 0x2222eeff, 0x3333ffff,
+0x4400ccff, 0x5511ddff, 0x6622eeff, 0x7733ffff,
+0x880088ff, 0x991199ff, 0xaa22aaff, 0xbb33bbff,
+0xcc0088ff, 0xdd1199ff, 0xee22aaff, 0xff33bbff,
+0x8800ccff, 0x9911ddff, 0xaa22eeff, 0xbb33ffff,
+0xcc00ccff, 0xdd11ddff, 0xee22eeff, 0xff33ffff,
+0x4488ff, 0x115599ff, 0x2266aaff, 0x3377bbff,
+0x444488ff, 0x555599ff, 0x6666aaff, 0x7777bbff,
+0x44ccff, 0x1155ddff, 0x2266eeff, 0x3377ffff,
+0x4444ccff, 0x5555ddff, 0x6666eeff, 0x7777ffff,
+0x884488ff, 0x995599ff, 0xaa66aaff, 0xbb77bbff,
+0xcc4488ff, 0xdd5599ff, 0xee66aaff, 0xff77bbff,
+0x8844ccff, 0x9955ddff, 0xaa66eeff, 0xbb77ffff,
+0xcc44ccff, 0xdd55ddff, 0xee66eeff, 0xff77ffff,
+0x8888ff, 0x119999ff, 0x22aaaaff, 0x33bbbbff,
+0x448888ff, 0x559999ff, 0x66aaaaff, 0x77bbbbff,
+0x88ccff, 0x1199ddff, 0x22aaeeff, 0x33bbffff,
+0x4488ccff, 0x5599ddff, 0x66aaeeff, 0x77bbffff,
+0x888888ff, 0x999999ff, 0xaaaaaaff, 0xbbbbbbff,
+0xcc8888ff, 0xdd9999ff, 0xeeaaaaff, 0xffbbbbff,
+0x8888ccff, 0x9999ddff, 0xaaaaeeff, 0xbbbbffff,
+0xcc88ccff, 0xdd99ddff, 0xeeaaeeff, 0xffbbffff,
+0xcc88ff, 0x11dd99ff, 0x22eeaaff, 0x33ffbbff,
+0x44cc88ff, 0x55dd99ff, 0x66eeaaff, 0x77ffbbff,
+0xccccff, 0x11ddddff, 0x22eeeeff, 0x33ffffff,
+0x44ccccff, 0x55ddddff, 0x66eeeeff, 0x77ffffff,
+0x88cc88ff, 0x99dd99ff, 0xaaeeaaff, 0xbbffbbff,
+0xcccc88ff, 0xdddd99ff, 0xeeeeaaff, 0xffffbbff,
+0x88ccccff, 0x99ddddff, 0xaaeeeeff, 0xbbffffff,
+0xccccccff, 0xddddddff, 0xeeeeeeff, 0xffffffff
+};
+
+struct rosprite_file_context* rosprite_create_file_context(FILE* f)
+{
+	struct rosprite_file_context* ctx = malloc(sizeof(struct rosprite_file_context));
+	ctx->f = f;
+	return ctx;
+}
+
+void rosprite_destroy_file_context(struct rosprite_file_context* ctx)
+{
+	free(ctx);
+}
+
+int rosprite_file_reader(uint8_t* buf, size_t count, void* ctx)
+{
+	return fread(buf, 1 /*size*/, count, ((struct rosprite_file_context*) ctx)->f);
+}
+
+/* TODO: get rid of this method */
+uint32_t sprite_read_word(reader reader, void* ctx)
+{
+	unsigned char b[4];
+	
+	if (reader(b, 4, ctx) < 4) {
+		printf("Unexpected EOF\n"); /* TODO, have better error handling, don't exit here */
+		exit(EXIT_FAILURE);
+	}
+
+	return BTUINT(b);
+}
+
+static struct rosprite_mode sprite_get_mode(uint32_t spriteMode)
+{
+	struct rosprite_mode mode;
+
+	uint32_t spriteType = (spriteMode & 0x78000000) >> 27; /* preserve bits 27-30 only */
+
+	if (spriteType != 0) {
+		bool hasEightBitAlpha = (spriteMode & 0x80000000) >> 31; /* bit 31 */
+		/* new modes have 1bpp masks (PRM5a-111)
+		 * unless bit 31 is set (http://select.riscos.com/prm/graphics/sprites/alphachannel.html)
+		 */
+		mode.maskbpp = (hasEightBitAlpha ? 8 : 1);
+		mode.mask_width = mode.maskbpp;
+		mode.xdpi = (spriteMode & 0x07ffc000) >> 14; /* preserve bits 14-26 only */
+		mode.ydpi = (spriteMode & 0x00003ffe) >> 1; /* preserve bits 1-13 only */
+
+		mode.color_model = rosprite_rgb;
+		switch (spriteType) {
+		case 1:
+			mode.colorbpp = 1; break;
+		case 2:
+			mode.colorbpp = 2; break;
+		case 3:
+			mode.colorbpp = 4; break;
+		case 4:
+			mode.colorbpp = 8; break;
+		case 5:
+			mode.colorbpp = 16; break;
+		case 6:
+			mode.colorbpp = 32; break;
+		case 7:
+			mode.colorbpp = 32;
+			mode.color_model = rosprite_cmyk;
+			break;
+		case 8:
+			mode.colorbpp = 24; break;
+		default:
+			assert(false);
+		}
+	} else {
+		/* clone station mode and return */
+		assert(spriteMode < 256); /* don't think you can have modes over 255? */
+		assert(oldmodes[spriteMode].colorbpp > 0); 
+
+		mode = oldmodes[spriteMode];
+	}
+
+	/* illegal mode check */
+	assert(mode.colorbpp > 0);
+	assert(mode.xdpi > 0);
+	assert(mode.ydpi > 0);
+
+	return mode;
+}
+
+static uint32_t sprite_palette_lookup(struct rosprite* sprite, uint32_t pixel)
+{
+	uint32_t translated_pixel;
+	 /* because we're dealing with 8bpp or less */
+	if (sprite->has_palette) {
+		assert(pixel <= sprite->palettesize); /* TODO: what to do if your color depth is bigger than palette? */
+		translated_pixel = sprite->palette[pixel];
+	} else {
+		switch (sprite->mode.colorbpp) {
+		case 8:
+			assert(pixel < 256);
+			translated_pixel = sprite_8bpp_palette[pixel];
+			break;
+		case 4:
+			assert(pixel < 16);
+			translated_pixel = sprite_4bpp_palette[pixel];
+			break;
+		case 2:
+			assert(pixel < 4);
+			translated_pixel = sprite_2bpp_palette[pixel];
+			break;
+		case 1:
+			assert(pixel < 2);
+			translated_pixel = sprite_1bpp_palette[pixel];
+			break;
+		default:
+			assert(false);
+		}
+	}
+	return translated_pixel;
+}
+
+static inline uint32_t sprite_cmyk_to_rgb(uint32_t cmyk)
+{
+        uint8_t c = cmyk & 0xff;
+        uint8_t m = (cmyk & 0xff00) >> 8;
+        uint8_t y = (cmyk & 0xff0000) >> 16;
+        uint8_t k = cmyk >> 24;
+ 
+        /* Convert to CMY colourspace */
+        uint8_t C = c + k;
+        uint8_t M = m + k;
+        uint8_t Y = y + k;
+ 
+        /* And to RGB */
+        uint8_t r = 255 - C;
+        uint8_t g = 255 - M;
+        uint8_t b = 255 - Y;
+ 
+        return r << 24 | g << 16 | b << 8;
+}
+
+static uint32_t sprite_upscale_color(uint32_t pixel, struct rosprite_mode* mode, bool* has_alpha_pixel_data)
+{
+	switch (mode->colorbpp) {
+	case 32:
+		if (mode->color_model == rosprite_rgb) {
+			/* swap from 0xAABBGGRR to 0xRRGGBBAA */
+			pixel = BSWAP(pixel);
+
+			uint8_t alpha = pixel & 0xff;
+			if (alpha == 0x00) {
+				if (!(*has_alpha_pixel_data)) {
+					pixel = pixel | 0xff;
+				}
+			} else {
+				*has_alpha_pixel_data = true;
+			}
+			return pixel;
+		} else {
+			return sprite_cmyk_to_rgb(pixel);
+		}
+	case 24:
+		/* reverse byte order */
+		return BSWAP(pixel);
+	case 16:
+		/* incoming format is b_00000000000000000bbbbbgggggrrrrr */
+		{
+			uint8_t red   = pixel & 31;
+			uint8_t green = (pixel & (31 << 5)) >> 5;
+			uint8_t blue  = (pixel & (31 << 10)) >> 10;
+
+			/* sanity check */
+			assert(red < 32);
+			assert(green < 32);
+			assert(blue < 32);
+
+			pixel =   (sprite_16bpp_translate[red] << 24)
+					| (sprite_16bpp_translate[green] << 16)
+					| (sprite_16bpp_translate[blue] << 8);
+		return pixel;
+		}
+	case 8:
+	case 4:
+	case 2:
+	case 1:
+		assert(false); /* shouldn't need to call for <= 8bpp, since a palette lookup will return 32bpp */
+	default:
+		assert(false); /* unknown bpp */
+	}
+}
+
+static inline void sprite_fix_alpha(uint32_t* image, uint32_t pixels)
+{
+	for (uint32_t i = 0; i <= pixels; i++) {
+		image[i] = image[i] & 0xffffff00;
+	}
+}
+
+static struct rosprite_mask_state* sprite_init_mask_state(struct rosprite* sprite, struct rosprite_header* header, uint8_t* mask)
+{
+	struct rosprite_mask_state* mask_state = malloc(sizeof(struct rosprite_mask_state));
+
+	mask_state->x = header->first_used_bit;
+	mask_state->y = 0;
+	mask_state->first_used_bit = header->first_used_bit;
+	mask_state->row_max_bit = sprite->width * sprite->mode.mask_width;
+	mask_state->height = sprite->height;
+	mask_state->bpp = sprite->mode.mask_width;
+	mask_state->current_word = BTUINT(mask);
+	mask_state->current_byte_index = 4;
+
+	return mask_state;
+}
+
+/* Get the next mask byte.
+ * Mask of 0xff denotes 100% opaque, 0x00 denotes 100% transparent
+ */
+static uint32_t sprite_next_mask_pixel(uint8_t* mask, struct rosprite_mask_state* mask_state)
+{
+	/* a 1bpp mask (for new mode sprites), each row is word aligned (therefore potential righthand wastage */	
+	const uint32_t bitmask = (1 << mask_state->bpp) - 1;
+	const uint32_t offset_into_word = mask_state->x % 32;
+	uint32_t pixel = (mask_state->current_word & (bitmask << offset_into_word)) >> offset_into_word;
+
+	if (mask_state->x + mask_state->bpp < mask_state->row_max_bit && offset_into_word + mask_state->bpp == 32) {
+		mask_state->current_word = BTUINT((mask + mask_state->current_byte_index));
+		mask_state->current_byte_index += 4;
+	}
+
+	mask_state->x += mask_state->bpp;
+	if (mask_state->x >= mask_state->row_max_bit) {
+		mask_state->x = mask_state->first_used_bit;
+
+		if (mask_state->y + 1 < mask_state->height) {
+			mask_state->current_word = BTUINT((mask + mask_state->current_byte_index));
+			mask_state->current_byte_index += 4;
+		}
+
+		mask_state->y++;
+	}
+
+	/*
+	 * if the mask is 1bpp, make sure the whole byte is 0x00 or 0xff
+	 */
+	if (mask_state->bpp < 8) {
+		pixel = (pixel & 1) ? 0xff : 0x00;
+	}
+
+	return pixel;
+}
+
+static void sprite_load_high_color(uint8_t* image_in, uint8_t* mask, struct rosprite* sprite, struct rosprite_header* header)
+{
+	struct rosprite_mask_state* mask_state = NULL;
+	if (sprite->has_mask) mask_state = sprite_init_mask_state(sprite, header, mask);
+
+	sprite->image = malloc(sprite->width * sprite->height * 4); /* all image data is 32bpp going out */
+
+	uint32_t currentByteIndex = 0;
+	const uint32_t bpp = sprite->mode.colorbpp;
+	const uint32_t bytesPerPixel = bpp / 8;
+	const uint32_t row_max_bit = header->width_words * 32 - (31 - header->last_used_bit); /* Last used bit in row */
+
+	bool has_alpha_pixel_data = false;
+
+	/* Spec says that there must be no left-hand wastage */
+	assert(header->first_used_bit == 0);
+	
+	for (uint32_t y = 0; y < sprite->height; y++) {
+		uint32_t x_pixels = 0;
+		for (uint32_t x = 0; x < row_max_bit; x += bpp) {
+			uint32_t pixel = 0;
+			for (uint32_t j = 0; j < bytesPerPixel; j++) {
+				uint8_t b = image_in[currentByteIndex++];
+				pixel = pixel | (b << (j * 8));
+			}
+			
+			bool old_has_alpha = has_alpha_pixel_data;
+			pixel = sprite_upscale_color(pixel, &(sprite->mode), &has_alpha_pixel_data);
+			if (old_has_alpha != has_alpha_pixel_data) {
+				sprite_fix_alpha(sprite->image, (y * sprite->width) + x_pixels - 1);
+			}
+			if (sprite->has_mask) {
+				uint8_t mask_pixel = sprite_next_mask_pixel(mask, mask_state);
+				pixel = (pixel & 0xffffff00) | mask_pixel;
+			}
+			sprite->image[y*sprite->width + x_pixels] = pixel;
+			x_pixels++;
+		}
+
+		/* Ensure byte index is pointing at start of next row */
+		if (y + 1 < sprite->height) {
+			currentByteIndex = (currentByteIndex + 3) & ~3; /* Round up to next multiple of 4 */
+		}
+	}
+
+	if (sprite->has_mask) free(mask_state);
+}
+
+static void sprite_load_low_color(uint8_t* image_in, uint8_t* mask, struct rosprite* sprite, struct rosprite_header* header)
+{
+	struct rosprite_mask_state* mask_state = NULL;
+	if (sprite->has_mask) mask_state = sprite_init_mask_state(sprite, header, mask);
+
+	sprite->image = malloc(sprite->width * sprite->height * 4); /* all image data is 32bpp going out */
+
+	const uint32_t bpp = sprite->mode.colorbpp;
+	const uint32_t row_max_bit = header->width_words * 32 - (31 - header->last_used_bit); /* Last used bit in row */
+	const uint32_t bitmask = (1 << bpp) - 1; /* creates a mask of 1s that is bpp bits wide */
+
+	uint32_t current_byte_index = 0;
+	uint32_t currentword = BTUINT((image_in + current_byte_index));
+	current_byte_index += 4;
+	
+	for (uint32_t y = 0; y < sprite->height; y++) {
+		uint32_t x_pixels = 0;
+		for (uint32_t x = header->first_used_bit; x < row_max_bit ; x += bpp) {
+			const uint32_t offset_into_word = x % 32;
+
+			uint32_t pixel = (currentword & (bitmask << offset_into_word)) >> offset_into_word;
+			pixel = sprite_palette_lookup(sprite, pixel); /* lookup returns 32bpp */
+			if (sprite->has_mask) {
+				uint8_t mask_pixel = sprite_next_mask_pixel(mask, mask_state);
+				pixel = (pixel & 0xffffff00) | mask_pixel;
+			}
+			sprite->image[y*sprite->width + x_pixels] = pixel;
+			x_pixels++;
+
+			/* If we're not at the end of the row and we've processed all of this word, fetch the next one */
+			if (x + bpp < row_max_bit && offset_into_word + bpp == 32) {
+				currentword = BTUINT((image_in + current_byte_index));
+				current_byte_index += 4;
+			}
+		}
+
+		/* Advance to first word of next row */
+		if (y + 1 < sprite->height) {
+			currentword = BTUINT((image_in + current_byte_index));
+			current_byte_index += 4;
+		}
+	}
+
+	if (sprite->has_mask) free(mask_state);
+}
+
+struct rosprite* sprite_load_sprite(reader reader, void* ctx)
+{
+	uint32_t nextSpriteOffset = sprite_read_word(reader, ctx);
+
+	struct rosprite* sprite = malloc(sizeof(struct rosprite));
+	struct rosprite_header* header = malloc(sizeof(struct rosprite_header));
+
+	reader(sprite->name, 12, ctx);
+	sprite->name[12] = '\0';
+
+	header->width_words     = sprite_read_word(reader, ctx) + 1; /* file has width - 1 and height - 1 */
+	sprite->height          = sprite_read_word(reader, ctx) + 1;
+	header->first_used_bit  = sprite_read_word(reader, ctx); /* old format only (spriteType = 0) */
+	header->last_used_bit   = sprite_read_word(reader, ctx);
+
+	uint32_t imageOffset    = sprite_read_word(reader, ctx);
+	assert(imageOffset >= 44); /* should never be smaller than the size of the header) */
+
+	uint32_t maskOffset     = sprite_read_word(reader, ctx);
+	uint32_t spriteModeWord = sprite_read_word(reader, ctx);
+
+	sprite->mode = sprite_get_mode(spriteModeWord);
+
+	/* TODO left-hand wastage */
+	
+	assert((header->last_used_bit + 1) % sprite->mode.colorbpp == 0);
+	/*assert(header->width_words % sprite->mode->colorbpp == 0);*/
+	sprite->width = (header->width_words * 32 - header->first_used_bit - (31 - header->last_used_bit)) / sprite->mode.colorbpp;
+
+	sprite->palettesize     = imageOffset - 44;
+	sprite->has_palette     = (sprite->palettesize > 0);
+
+
+	/* sprite has no mask if imageOffset == maskOffset */
+	if (imageOffset == maskOffset) {
+		sprite->has_mask   = false;
+		header->image_size = nextSpriteOffset - 44 - sprite->palettesize;
+		header->mask_size  = 0;
+	} else {
+		sprite->has_mask   = true;
+		header->image_size = maskOffset - imageOffset;
+		header->mask_size  = nextSpriteOffset - 44 - sprite->palettesize - header->image_size;
+	}
+	
+	if (sprite->has_palette) {
+		assert(sprite->palettesize % 8 == 0);
+		sprite->palette = malloc(sizeof(uint32_t) * sprite->palettesize);
+		uint32_t paletteEntries = sprite->palettesize / 8;
+
+		/* Each palette entry is two words big
+		 * The second word is a duplicate of the first
+		 * I think this is in case you ever wanted flashing colours
+		 * PRM1-730
+		 */
+		for (uint32_t j = 0; j < paletteEntries; j++) {
+			uint32_t word1 = sprite_read_word(reader, ctx);
+			uint32_t word2 = sprite_read_word(reader, ctx);
+			assert(word1 == word2); /* TODO: if they aren't, START FLASHING */
+			
+			/* swap rr and bb parts -- PRM1-731 */
+			uint32_t entry = ((word1 & 0xff000000) >> 16) | (word1 & 0x00ff0000) | ((word1 & 0x0000ff00) << 16) | 0xff;
+			sprite->palette[j] = entry;
+		}
+	}
+
+	uint8_t* image = malloc(header->image_size);
+	reader(image, header->image_size, ctx);
+
+	uint8_t* mask = NULL;
+	if (sprite->has_mask) {
+		mask = malloc(header->mask_size);
+		reader(mask, header->mask_size, ctx);
+	}
+
+	/* sanity check image_size */
+	assert((header->width_words) * 4 * (sprite->height) == header->image_size);
+	/* TODO: sanity check mask_size */
+	if (sprite->mode.colorbpp > 8) {
+		sprite_load_high_color(image, mask, sprite, header);
+	} else {
+		sprite_load_low_color(image, mask, sprite, header);
+	}
+
+	free(image);
+	free(mask);
+	free(header);
+
+	return sprite;
+}
+
+struct rosprite_area* rosprite_load_file(reader reader, void* ctx)
+{
+	struct rosprite_area* sprite_area = malloc(sizeof(struct rosprite_area));
+
+	sprite_area->sprite_count = sprite_read_word(reader, ctx);
+
+	uint32_t firstSpriteOffset = sprite_read_word(reader, ctx);
+	/*uint32_t firstFreeWordOffset = */sprite_read_word(reader, ctx); /* TODO: use this for some sanity checking? */
+	sprite_area->extension_size = 16 - firstSpriteOffset;
+
+	sprite_area->extension_words = NULL;
+	if (sprite_area->extension_size > 0) {
+		sprite_area->extension_words = malloc(sprite_area->extension_size); /* where to free() this? */
+		reader(sprite_area->extension_words, (size_t) (sprite_area->extension_size), ctx); /* TODO: check return value */
+	}
+
+	sprite_area->sprites = malloc(sizeof(struct rosprite*) * sprite_area->sprite_count); /* allocate array of pointers */
+	for (uint32_t i = 0; i < sprite_area->sprite_count; i++) {
+		struct rosprite* sprite = sprite_load_sprite(reader, ctx);
+		sprite_area->sprites[i] = sprite;
+	}
+
+	return sprite_area;
+}
+
+void rosprite_destroy_sprite_area(struct rosprite_area* sprite_area)
+{
+	for (uint32_t i = 0; i < sprite_area->sprite_count; i++) {
+		struct rosprite* sprite = sprite_area->sprites[i];
+		if (sprite->has_palette) free(sprite->palette);
+		free(sprite->image);
+		free(sprite);
+	}
+
+	free(sprite_area->sprites);
+	if (sprite_area->extension_size > 0) free(sprite_area->extension_words);
+	free(sprite_area);
+}
+
+struct rosprite_palette* rosprite_load_palette(reader reader, void* ctx)
+{
+	/* Palette file is in groups of 6 bytes, each is a VDU 19 (set palette)
+	 * http://www.drobe.co.uk/show_manual.php?manual=/sh-cgi?manual=Vdu%26page=19 */
+
+	/* TODO: currently assume palette has linear entries (2nd byte in is 00, 01, 02 etc) */
+	struct rosprite_palette* palette = malloc(sizeof(struct rosprite_palette));
+
+	palette->palette = malloc(sizeof(uint32_t) * 256); /* allocate 256 whether we need them all or not */
+
+	uint32_t c = 0;
+	uint8_t b[6];
+
+	unsigned int bytesRead = reader(b, 6, ctx);
+	assert(bytesRead % 6 == 0);
+	while (bytesRead == 6) {
+		assert(b[0] == 19); /* VDU 19 */
+
+		/* only process logical colours */
+		if (b[2] == 16) {
+			/*assert(c == b[1]);*/
+	
+			uint32_t entry = (b[3] << 24) | (b[4] << 16) | (b[5] << 8) | 0xff; /* last byte is alpha */
+			palette->palette[c] = entry;
+	
+			c++;
+			assert(c <= 256);
+		}
+
+		bytesRead = reader(b, 6, ctx);
+		assert(bytesRead % 6 == 0);
+	}
+
+	palette->size = c;
+
+	return palette;
+}
+
+void rosprite_destroy_palette(struct rosprite_palette* palette)
+{
+	free(palette->palette);
+	free(palette);
+}